HOKU SCIENTIFIC, INC.

Exhibit 10.13

HOKU SCIENTIFIC, INC.

2005 NON-EMPLOYEE DIRECTORS’ STOCK OPTION PLAN

ADOPTED: MARCH 24, 2005

APPROVED BY STOCKHOLDERS: JULY 11, 2005

(a) Eligible Option Recipients. The persons eligible to receive Options are the Non-Employee Directors of the Company.

(b) General Purpose. The Company, by means of the Plan, seeks to retain the services of its Non-Employee Directors, to secure and retain the services of new Non-Employee Directors and to provide incentives for such persons to exert maximum efforts for the success of the Company and any Affiliate by giving them an opportunity to benefit from increases in value of the Common Stock through the automatic grant of Nonstatutory Stock Options.

As used in the Plan, the following definitions shall apply to the capitalized terms indicated below:

(a) “Accountant” means the independent public accountants of the Company.

(b) “Affiliate” means (i) any corporation (other than the Company) in an unbroken chain of corporations ending with the Company, provided each corporation in the unbroken chain (other than the Company) owns, at the time of the determination, stock possessing fifty percent (50%) or more of the total combined voting power of all classes of stock in one of the other corporations in such chain, and (ii) any corporation (other than the Company) in an unbroken chain of corporations beginning with the Company, provided each corporation (other than the last corporation) in the unbroken chain owns, at the time of the determination, stock possessing fifty percent (50%) or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. The Board shall have the authority to determine (i) the time or times at which the ownership tests are applied, and (ii) whether “Affiliate” includes entities other than corporations within the foregoing definition.

(c) “Annual Grant” means an Option granted annually to all Non-Employee Directors who meet the specified criteria pursuant to Section 6(b).

(d) “Annual Meeting” means the annual meeting of the stockholders of the Company.

(e) “Board” means the Board of Directors of the Company.

(f) “Capitalization Adjustment” has the meaning ascribed to that term in Section 11(a).

(g) “Change in Control” means the occurrence, in a single transaction or in a series of related transactions, of any one or more of the following events:

(i) any Exchange Act Person becomes the Owner, directly or indirectly, of securities of the Company representing more than fifty percent (50%) of the combined voting power of the Company’s then outstanding securities other than by virtue of a merger, consolidation or similar transaction. Notwithstanding the foregoing, a Change in Control shall not be deemed to occur (A) on account of the acquisition of securities of the Company by an investor, any affiliate thereof or any other Exchange Act Person from the Company in a transaction or series of related transactions the primary purpose of which is to obtain financing for the Company through the issuance of equity securities or (B) solely because the level of Ownership held by any Exchange Act Person (the “Subject Person”) exceeds the designated percentage threshold of the outstanding voting securities as a result of a repurchase or other acquisition of voting securities by the Company reducing the number of shares outstanding, provided that if a Change in Control would occur (but for the operation of this sentence) as a result of the acquisition of voting securities by the Company, and after such share acquisition, the Subject Person becomes the Owner of any additional voting securities that, assuming the repurchase or other acquisition had not occurred, increases the percentage of the then outstanding voting securities Owned by the Subject Person over the designated percentage threshold, then a Change in Control shall be deemed to occur;

(ii) there is consummated a merger, consolidation or similar transaction involving (directly or indirectly) the Company and, immediately after the consummation of such merger, consolidation or similar transaction, the stockholders of the Company immediately prior thereto do not Own, directly or indirectly, either (A) outstanding voting securities representing more than fifty percent (50%) of the combined outstanding voting power of the surviving Entity in such merger, consolidation or similar transaction or (B) more than fifty percent (50%) of the combined outstanding voting power of the parent of the surviving Entity in such merger, consolidation or similar transaction, in each case in substantially the same proportions as their Ownership of the outstanding voting securities of the Company immediately prior to such transaction;

(iii) the stockholders of the Company approve or the Board approves a plan of complete dissolution or liquidation of the Company, or a complete dissolution or liquidation of the Company shall otherwise occur;

(iv) there is consummated a sale, lease, exclusive license or other disposition of all or substantially all of the consolidated assets of the Company and its Subsidiaries, other than a sale, lease, license or other disposition of all or substantially all of the consolidated assets of the Company and its Subsidiaries to an Entity, more than fifty percent (50%) of the combined voting power of the voting securities of which are Owned by stockholders of the Company in substantially the same proportions as their Ownership of the outstanding voting securities of the Company immediately prior to such sale, lease, license or other disposition; or

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(v) individuals who, on the date this Plan is adopted by the Board, are members of the Board (the “Incumbent Board”) cease for any reason to constitute at least a majority of the members of the Board; provided, however, that if the appointment or election (or nomination for election) of any new Board member was approved or recommended by a majority vote of the members of the Incumbent Board then still in office, such new member shall, for purposes of this Plan, be considered as a member of the Incumbent Board.

The term Change in Control shall not include a sale of assets, merger or other transaction effected exclusively for the purpose of changing the domicile of the Company.

Notwithstanding the foregoing or any other provision of this Plan, the definition of Change in Control (or any analogous term) in an individual written agreement between the Company or any Affiliate and the Optionholder shall supersede the foregoing definition with respect to Options subject to such agreement; provided, however, that if no definition of Change in Control or any analogous term is set forth in such an individual written agreement, the foregoing definition shall apply.

(h) “Code” means the Internal Revenue Code of 1986, as amended.

(i) “Common Stock” means the common stock of the Company.

(j) “Company” means Hoku Scientific, Inc., a Delaware corporation.

(k) “Consultant” means any person, including an advisor, who is (i) engaged by the Company or an Affiliate to render consulting or advisory services and is compensated for such services, or (ii) serving as a member of the Board of Directors of an Affiliate and is compensated for such services. However, service solely as a Director, or payment of a fee for such service, shall not cause a Director to be considered a “Consultant” for purposes of the Plan.

(l) “Continuous Service” means that the Optionholder’s service with the Company or an Affiliate, whether as an Employee, Director or Consultant, is not interrupted or terminated. A change in the capacity in which the Optionholder renders service to the Company or an Affiliate as an Employee, Consultant or Director or a change in the entity for which the Optionholder renders such service, provided that there is no interruption or termination of the Optionholder’s service with the Company or an Affiliate, shall not terminate an Optionholder’s Continuous Service. For example, a change in status from a Non-Employee Director of the Company to a Consultant of an Affiliate or an Employee of the Company will not constitute an interruption of Continuous Service. To the extent permitted by law, the Board or the chief executive officer of the Company, in that party’s sole discretion, may determine whether Continuous Service shall be considered interrupted in the case of any leave of absence approved by that party, including sick leave, military leave or any other personal leave. Notwithstanding the foregoing, a leave of absence shall be treated as Continuous Service for purposes of vesting in an Option only to such extent as may be provided in the Company’s leave of absence policy or in the written terms of the Optionholder’s leave of absence.

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(m) “Corporate Transaction” means the occurrence, in a single transaction or in a series of related transactions, of any one or more of the following events:

(i) a sale or other disposition of all or substantially all, as determined by the Board in its sole discretion, of the consolidated assets of the Company and its Subsidiaries;

(ii) a sale or other disposition of at least ninety percent (90%) of the outstanding securities of the Company;

(iii) the consummation of a merger, consolidation or similar transaction following which the Company is not the surviving corporation; or

(iv) the consummation of a merger, consolidation or similar transaction following which the Company is the surviving corporation but the shares of Common Stock outstanding immediately preceding the merger, consolidation or similar transaction are converted or exchanged by virtue of the merger, consolidation or similar transaction into other property, whether in the form of securities, cash or otherwise.

(n) “Director” means a member of the Board.

(o) “Disability” means the permanent and total disability of a person within the meaning of Section 22(e)(3) of the Code.

(p) “Employee” means any person employed by the Company or an Affiliate. However, service solely as a Director, or payment of a fee for such services, shall not cause a Director to be considered an “Employee” for purposes of the Plan.

(q) “Entity” means a corporation, partnership or other entity.

(r) “Exchange Act” means the Securities Exchange Act of 1934, as amended.

(s) “Exchange Act Person” means any natural person, Entity or “group” (within the meaning of Section 13(d) or 14(d) of the Exchange Act), except that “Exchange Act Person” shall not include (i) the Company or any Subsidiary of the Company, (ii) any employee benefit plan of the Company or any Subsidiary of the Company or any trustee or other fiduciary holding securities under an employee benefit plan of the Company or any Subsidiary of the Company, (iii) an underwriter temporarily holding securities pursuant to an offering of such securities, (iv) an Entity Owned, directly or indirectly, by the stockholders of the Company in substantially the same proportions as their Ownership of stock of the Company; or (v) any natural person, Entity or “group” (within the meaning of Section 13(d) or 14(d) of the Exchange Act) that, as of the effective date of the Plan as set forth in Section 14, is the Owner, directly or indirectly, of securities of the Company representing more than fifty percent (50%) of the combined voting power of the Company’s then outstanding securities.

(t) “Fair Market Value” means, as of any date, the value of the Common Stock determined as follows:

(i) If the Common Stock is listed on any established stock exchange or traded on the Nasdaq National Market or the Nasdaq SmallCap Market, the Fair Market Value of a share of Common Stock shall be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on such exchange or market (or the exchange or market with the

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greatest volume of trading in the Common Stock) on the last market trading day prior to the day of determination, as reported in The Wall Street Journal or such other source as the Board deems reliable.

(ii) In the absence of such markets for the Common Stock, the Fair Market Value shall be determined by the Board in good faith.

(u) “Initial Grant” means an Option granted to a Non-Employee Director who meets the specified criteria pursuant to Section 6(a).

(v) “IPO Date” means the date of the underwriting agreement between the Company and the underwriter(s) managing the initial public offering of the Common Stock, pursuant to which the Common Stock is priced for the initial public offering.

(w) “Non-Employee Director” means a Director who is not an Employee.

(x) “Nonstatutory Stock Option” means an Option not intended to qualify as an incentive stock option within the meaning of Section 422 of the Code and the regulations promulgated thereunder.

(y) “Officer” means a person who is an officer of the Company within the meaning of Section 16 of the Exchange Act and the rules and regulations promulgated thereunder.

(z) “Option” means a Nonstatutory Stock Option granted pursuant to the Plan.

(aa) “Option Agreement” means a written agreement between the Company and an Optionholder evidencing the terms and conditions of an individual Option grant. Each Option Agreement shall be subject to the terms and conditions of the Plan.

(bb) “Optionholder” means a person to whom an Option is granted pursuant to the Plan or, if applicable, such other person who holds an outstanding Option.

(cc) “Own,” “Owned,” “Owner,” “Ownership” A person or Entity shall be deemed to “Own,” to have “Owned,” to be the “Owner” of, or to have acquired “Ownership” of securities if such person or Entity, directly or indirectly, through any contract, arrangement, understanding, relationship or otherwise, has or shares voting power, which includes the power to vote or to direct the voting, with respect to such securities.

(dd) “Plan” means this Hoku Scientific, Inc. 2005 Non-Employee Directors’ Stock Option Plan.

(ee) “Rule 16b-3” means Rule 16b-3 promulgated under the Exchange Act or any successor to Rule 16b-3, as in effect from time to time.

(ff) “Securities Act” means the Securities Act of 1933, as amended.

(gg) “Subsidiary” means, with respect to the Company, (i) any corporation of which more than fifty percent (50%) of the outstanding capital stock having ordinary voting power to

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elect a majority of the board of directors of such corporation (irrespective of whether, at the time, stock of any other class or classes of such corporation shall have or might have voting power by reason of the happening of any contingency) is at the time, directly or indirectly, Owned by the Company, and (ii) any partnership in which the Company has a direct or indirect interest (whether in the form of voting or participation in profits or capital contribution) of more than fifty percent (50%).

(a) Administration by Board. The Board shall administer the Plan. The Board may not delegate administration of the Plan.

(b) Powers of Board. The Board shall have the power, subject to, and within the limitations of, the express provisions of the Plan:

(i) To determine the provisions of each Option to the extent not specified in the Plan.

(ii) To construe and interpret the Plan and Options granted under it, and to establish, amend and revoke rules and regulations for its administration. The Board, in the exercise of this power, may correct any defect, omission or inconsistency in the Plan or in any Option Agreement, in a manner and to the extent it shall deem necessary or expedient to make the Plan fully effective.

(iii) To amend the Plan or an Option as provided in Section 12.

(iv) To terminate or suspend the Plan as provided in Section 13.

(v) Generally, to exercise such powers and to perform such acts as the Board deems necessary or expedient to promote the best interests of the Company and that are not in conflict with the provisions of the Plan.

(c) Effect of Board’s Decision. All determinations, interpretations and constructions made by the Board in good faith shall not be subject to review by any person and shall be final, binding and conclusive on all persons.

(a) Share Reserve. Subject to the provisions of Section 11(a) relating to Capitalization Adjustments upon changes in the Common Stock, the Common Stock that may be issued pursuant to Options shall not exceed in the aggregate sixty-six thousand six hundred sixty-six (66,666) shares of Common Stock, plus an automatic annual increase beginning on April 1, 2006 and ending on (and including) April 1, 2014 equal to the number of shares subject to Options granted during the preceding fiscal year less the number of shares added back to the share reserve during the preceding fiscal year pursuant to the provisions of Section 4(b). Notwithstanding the foregoing, the Board may act, prior to the last day of any fiscal year of the Company, to increase the share reserve by such number of shares of Common Stock as the Board shall determine, which number shall be less than the amount described in the prior sentence.

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(b) Reversion of Shares to the Share Reserve. If an Option shall for any reason expire or otherwise terminate, in whole or in part, without having been exercised in full, the shares of Common Stock not acquired under such Option shall revert to and again become available for issuance under the Plan. If any shares subject to an Option are not delivered to an Optionholder because such shares are withheld for the payment of taxes or the Option is exercised through a reduction of shares subject to the Option (i.e., “net exercised”), the number of shares that are not delivered to the Optionholder shall remain available for issuance under the Plan. If the exercise price of an Option is satisfied by tendering shares of Common Stock held by the Optionholder (either by actual delivery or attestation), then the number of shares so tendered shall remain available for issuance under the Plan.

(c) Source of Shares. The stock issuable under the Plan shall be shares of authorized but unissued or reacquired Common Stock, including shares repurchased by the Company on the open market.

The Options shall automatically be granted under the Plan as set forth in Section 6 to all Non-Employee Directors who meet the specified criteria.

(a) Initial Grants. Without any further action of the Board, each person who after the IPO Date is elected or appointed for the first time to be a Non-Employee Director automatically shall, upon the date of his or her initial election or appointment to be a Non-Employee Director, be granted an Initial Grant to purchase twenty thousand (20,000) shares of Common Stock on the terms and conditions set forth herein.

(b) Annual Grants. Without any further action of the Board, on the date of each Annual Meeting, commencing with the Annual Meeting in 2006, each person who is then a Non-Employee Director and has served as a Non-Employee Director for at least six (6) months prior to such Annual Meeting shall automatically be granted an Annual Grant to purchase six thousand six hundred sixty-six (6,666) shares of Common Stock on the terms and conditions set forth herein.

Each Option shall be in such form and shall contain such terms and conditions as required by the Plan. Each Option shall contain such additional terms and conditions, not inconsistent with the Plan, as the Board shall deem appropriate. Each Option shall include (through incorporation of provisions hereof by reference in the Option or otherwise) the substance of each of the following provisions:

(a) Term. No Option shall be exercisable after the expiration of ten (10) years from the date it was granted.

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(b) Exercise Price. The exercise price of each Option shall be one hundred percent (100%) of the Fair Market Value of the Common Stock subject to the Option on the date the Option is granted.

(c) Consideration. The purchase price of Common Stock acquired pursuant to an Option may be paid, to the extent permitted by applicable law, in any combination of (i) cash or check, (ii) delivery to the Company (either by actual delivery or attestation) of shares of Common Stock held for more than six (6) months (or such longer or shorter period of time necessary to avoid a charge to earnings for financial accounting purposes), or (iii) to the extent permitted by law, pursuant to a program developed under Regulation T as promulgated by the Federal Reserve Board that, prior to the issuance of Common Stock, results in either the receipt of cash (or check) by the Company or the receipt of irrevocable instructions to pay the aggregate exercise price to the Company from the sales proceeds.

(d) Transferability. Except as otherwise provided for in this Section 7(d), an Option shall not be transferable except by will or by the laws of descent and distribution and shall be exercisable only by the Optionholder during the life of the Optionholder. However, an Option may be transferred for no consideration upon written consent of the Board if (i) at the time of transfer, a Form S-8 registration statement under the Securities Act is available for the issuance of shares by the Company upon the exercise of such transferred Option, or (ii) the transfer is to the Optionholder’s employer at the time of transfer or an affiliate of the Optionholder’s employer at the time of transfer. Any such transfer is subject to such limits as the Board may establish, and subject to the transferee agreeing to remain subject to all the terms and conditions applicable to the Option prior to such transfer. The forgoing right to transfer the Option shall apply to the right to consent to amendments to the Option Agreement for such Option. In addition, until the Optionholder transfers the Option, an Optionholder may, by delivering written notice to the Company, in a form provided by or otherwise satisfactory to the Company, designate a third party who, in the event of the death of the Optionholder, shall thereafter be entitled to exercise the Option.

(e) Vesting. Options shall vest as follows:

(i) Initial Grants. 1/36^th of the shares shall vest monthly over three (3) years.

(ii) Annual Grants. 1/12^th of the shares shall vest monthly commencing on the second anniversary of the date of grant.

(f) Early Exercise. The Option may, but need not, include a provision whereby the Optionholder may elect at any time before the Optionholder’s Continuous Service terminates to exercise the Option as to any part or all of the shares of Common Stock subject to the Option prior to the full vesting of the Option. Any unvested shares of Common Stock so purchased may be subject to a repurchase option in favor of the Company or to any other restriction the Board determines to be appropriate. The Company will not exercise its repurchase option until at least six (6) months (or such longer or shorter period of time required to avoid a charge to earnings for financial accounting purposes) have elapsed following exercise of the Option unless the Board otherwise specifically provides in the Option.

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(g) Termination of Continuous Service. In the event that an Optionholder’s Continuous Service terminates (other than upon the Optionholder’s death or Disability or upon a Change in Control), the Optionholder may exercise his or her Option (to the extent that the Optionholder was entitled to exercise such Option as of the date of termination of Continuous Service) but only within such period of time ending on the earlier of (i) the date three (3) months following the termination of the Optionholder’s Continuous Service (or such longer or shorter period specified in the Option Agreement), or (ii) the expiration of the term of the Option as set forth in the Option Agreement. If, after termination of Continuous Service, the Optionholder does not exercise his or her Option within the time specified herein or in the Option Agreement (as applicable), the Option shall terminate.

(h) Extension of Termination Date. If the exercise of the Option following the termination of the Optionholder’s Continuous Service (other than upon the Optionholder’s death or Disability or upon a Change in Control) would be prohibited at any time solely because the issuance of shares of Common Stock would violate the registration requirements under the Securities Act, then the Option shall terminate on the earlier of (i) the expiration of a period of three (3) months after the termination of the Optionholder’s Continuous Service during which the exercise of the Option would not be in violation of such registration requirements, or (ii) the expiration of the term of the Option as set forth in the Option Agreement.

(i) Disability of Optionholder. In the event that an Optionholder’s Continuous Service terminates as a result of the Optionholder’s Disability, the Optionholder may exercise his or her Option (to the extent that the Optionholder was entitled to exercise it as of the date of termination), but only within such period of time ending on the earlier of (i) the date twelve (12) months following such termination of Continuous Service, or (ii) the expiration of the term of the Option as set forth in the Option Agreement. If, after termination, the Optionholder does not exercise his or her Option within the time specified herein or in the Option Agreement, the Option shall terminate.

(j) Death of Optionholder. In the event that (i) an Optionholder’s Continuous Service terminates as a result of the Optionholder’s death, or (ii) the Optionholder dies within the three-month period after the termination of the Optionholder’s Continuous Service for a reason other than death, then the Option may be exercised (to the extent the Optionholder was entitled to exercise such Option as of the date of death) by the Optionholder’s estate, by a person who acquired the right to exercise the Option by bequest or inheritance or by a person designated to exercise the Option upon the Optionholder’s death, but only within the period ending on the earlier of (i) the date eighteen (18) months following the date of death, or (ii) the expiration of the term of such Option as set forth in the Option Agreement. If, after the Optionholder’s death, the Option is not exercised within the time specified herein, the Option shall terminate.

(k) Termination Upon Change in Control. In the event that an Optionholder’s Continuous Service terminates as of, or within twelve (12) months following a Change in Control, the Optionholder may exercise his or her Option (to the extent that the Optionholder was entitled to exercise such Option as of the date of termination of Continuous Service) within such period of time ending on the earlier of (i) the date twelve (12) months following the effective date of the Change in Control (or such longer or shorter period specified in the Option Agreement), or (ii) the expiration of the term of the Option as set forth in the Option Agreement.

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If, after termination of Continuous Service, the Optionholder does not exercise his or her Option within the time specified herein or in the Option Agreement (as applicable), the Option shall terminate.

The Company shall seek to obtain from each regulatory commission or agency having jurisdiction over the Plan such authority as may be required to grant Options and to issue and sell shares of Common Stock upon exercise of the Options; provided, however, that this undertaking shall not require the Company to register under the Securities Act the Plan, any Option or any Common Stock issued or issuable pursuant to any such Option. If, after reasonable efforts, the Company is unable to obtain from any such regulatory commission or agency the authority that counsel for the Company deems necessary for the lawful issuance and sale of Common Stock under the Plan, the Company shall be relieved from any liability for failure to issue and sell Common Stock upon exercise of such Options unless and until such authority is obtained.

Proceeds from the sale of shares of Common Stock pursuant to Options shall constitute general funds of the Company.

(a) Stockholder Rights. No Optionholder shall be deemed to be the holder of, or to have any of the rights of a holder with respect to, any shares of Common Stock subject to such Option unless and until such Optionholder has satisfied all requirements for exercise of the Option pursuant to its terms.

(b) No Service Rights. Nothing in the Plan, any instrument executed, or Option granted pursuant thereto shall confer upon any Optionholder any right to continue to serve the Company as a Non-Employee Director or shall affect the right of the Company or an Affiliate to terminate the service of a Director pursuant to the Bylaws of the Company or an Affiliate, and any applicable provisions of the corporate law of the state in which the Company or the Affiliate is incorporated, as the case may be.

(c) Investment Assurances. The Company may require an Optionholder, as a condition of exercising or acquiring Common Stock under any Option, (i) to give written assurances satisfactory to the Company as to the Optionholder’s knowledge and experience in financial and business matters and/or to employ a purchaser representative reasonably satisfactory to the Company who is knowledgeable and experienced in financial and business matters and that he or she is capable of evaluating, alone or together with the purchaser representative, the merits and risks of exercising the Option; and (ii) to give written assurances satisfactory to the Company stating that the Optionholder is acquiring the Common Stock subject to the Option for the Optionholder’s own account and not with any present intention of selling or otherwise distributing the Common Stock. The foregoing requirements, and any assurances given pursuant to such requirements, shall be inoperative if (i) the issuance of the shares upon the exercise or acquisition of Common Stock under the Option has been registered under a then currently effective registration statement under the Securities Act, or (ii) as to any particular

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requirement, a determination is made by counsel for the Company that such requirement need not be met in the circumstances under the then applicable securities laws. The Company may, upon advice of counsel to the Company, place legends on stock certificates issued under the Plan as such counsel deems necessary or appropriate in order to comply with applicable securities laws, including, but not limited to, legends restricting the transfer of the Common Stock.

(d) Withholding Obligations. The Optionholder may satisfy any federal, state or local tax withholding obligation relating to the exercise or acquisition of Common Stock under an Option by any of the following means (in addition to the Company’s right to withhold from any compensation paid to the Optionholder by the Company) or by a combination of such means: (i) tendering a cash payment; (ii) authorizing the Company to withhold shares from the shares of the Common Stock otherwise issuable to the Optionholder as a result of the exercise or acquisition of Common Stock under the Option; provided, however, that no shares of Common Stock are withheld with a value exceeding the minimum amount of tax required to be withheld by law; or (iii) delivering to the Company owned and unencumbered shares of the Common Stock.

(e) Electronic Delivery. Any reference herein to a “written” agreement or document shall include any agreement or document delivered electronically or posted on the Company’s intranet.

(a) Capitalization Adjustments. If any change is made in, or other events occur with respect to, the Common Stock subject to the Plan or subject to any Option after the effective date of the Plan set forth in Section 14 without the receipt of consideration by the Company (through merger, consolidation, reorganization, recapitalization, reincorporation, stock dividend, dividend in property other than cash, stock split, liquidating dividend, combination of shares, exchange of shares, change in corporate structure or other transaction not involving the receipt of consideration by the Company (each a “Capitalization Adjustment”)), the Board shall appropriately adjust: (i) the class(es) and maximum number of securities subject to the Plan pursuant to Section 4(a), (ii) the class(es) and maximum number of securities by which the share reserve is to increase automatically each year pursuant to Section 4(a), (iii) the class(es) and number of securities for which the nondiscretionary grants of Options are made pursuant to Section 6, and (iv) the class(es) and number of securities and price per share of stock subject to outstanding Options. The Board shall make such adjustments, and its determination shall be final, binding and conclusive. (Notwithstanding the foregoing, the conversion of any convertible securities of the Company shall not be treated as a transaction “without receipt of consideration” by the Company.)

(b) Dissolution or Liquidation. In the event of a dissolution or liquidation of the Company, all outstanding Options shall terminate immediately prior to the completion of such dissolution or liquidation.

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(c) Corporate Transaction.

(i) Options May Be Assumed. In the event of a Corporate Transaction, any surviving corporation or acquiring corporation (or the surviving or acquiring corporation’s parent company) may assume or continue any or all Options outstanding under the Plan or may substitute similar stock options for Options outstanding under the Plan (including but not limited to, options to acquire the same consideration paid to the stockholders of the Company pursuant to the Corporate Transaction), and any reacquisition or repurchase rights held by the Company in respect of Common Stock issued pursuant to Options may be assigned by the Company to the successor of the Company (or the successor’s parent company, if any), in connection with such Corporate Transaction. A surviving corporation or acquiring corporation not choose to assume or continue only a portion of an Option or substitute a similar option for only a portion of an Option.

(ii) Options Held by Active Optionholders. In the event of a Corporate Transaction in which the surviving corporation or acquiring corporation (or its parent company) does not assume or continue such outstanding Options or substitute similar stock options for such outstanding Options, then with respect to Options that have not been assumed, continued or substituted and that are held by Optionholders whose Continuous Service has not terminated prior to the effective time of the Corporate Transaction (referred to as the “Active Optionholders”), the vesting of such Options (and, if applicable, the time at which such Options may be exercised) shall (contingent upon the effectiveness of the Corporate Transaction) be accelerated in full to a date prior to the effective time of such Corporate Transaction as the Board shall determine (or, if the Board shall not determine such a date, to the date that is five (5) days prior to the effective time of the Corporate Transaction), and the Options shall terminate if not exercised (if applicable) at or prior to the effective time of the Corporate Transaction, and any reacquisition or repurchase rights held by the Company with respect to such Options shall lapse (contingent upon the effectiveness of the Corporate Transaction).

(iii) Options Held by Former Optionholders. In the event of a Corporate Transaction in which the surviving corporation or acquiring corporation (or its parent company) does not assume or continue such outstanding Options or substitute similar stock options for such outstanding Options, then with respect to any other Options that have not been assumed, continued or substituted and that are held by persons other than Active Optionholders, the vesting of such Options (and, if applicable, the time at which such Options may be exercised) shall not be accelerated unless otherwise provided in Section 11(d) or in a written agreement between the Company or any Affiliate and the holder of such Options, and such Options shall terminate if not exercised (if applicable) prior to the effective time of the Corporate Transaction; provided, however, that any reacquisition or repurchase rights held by the Company with respect to such Options shall not terminate and may continue to be exercised notwithstanding the Corporate Transaction.

(iv) Payment for Options in Lieu of Exercise. Notwithstanding the foregoing, in the event an Option will terminate if not exercised prior to the effective time of a Corporate Transaction, the Board may provide, in its sole discretion, that the holder of such Option may not exercise such Option but will receive a payment, in such form as may be determined by the Board, equal in value to the excess, if any, of (i) the value of the property the

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holder of the Option would have received upon the exercise of the Option, over (ii) the exercise price payable by the Optionholder in connection with such exercise.

(d) Change in Control. In the event that an Optionholder (i) is required to resign his or her position as a Non-Employee Director as a condition of a Change in Control, or (ii) is removed from his or her position as a Non-Employee Director in connection with a Change in Control, the outstanding Options held by such Optionholder shall become fully vested and exercisable immediately prior to the effectiveness of such resignation or removal (and contingent upon the effectiveness of such Change in Control).

(e) Parachute Payments.

(i) If the acceleration of the vesting and exercisability of Options provided for in Sections 11(c) and 11(d), together with payments and other benefits of an Optionholder, (collectively, the “Payment”) (i) constitute a “parachute payment” within the meaning of Section 280G of the Code, or any comparable successor provisions, and (ii) but for this Section 11(e) would be subject to the excise tax imposed by Section 4999 of the Code, or any comparable successor provisions (the “Excise Tax”), then such Payment shall be either (1) provided to such Optionholder in full, or (2) provided to such Optionholder as to such lesser extent that would result in no portion of such Payment being subject to the Excise Tax, whichever of the foregoing amounts, when taking into account applicable federal, state, local and foreign income and employment taxes, the Excise Tax, and any other applicable taxes, results in the receipt by such Optionholder, on an after-tax basis, of the greatest amount of the Payment, notwithstanding that all or some portion of the Payment may be subject to the Excise Tax.

(ii) Unless the Company and such Optionholder otherwise agree in writing, any determination required under this Section 11(e) shall be made in writing in good faith by the Accountant. If a reduction in the Payment is to be made as provided above, reductions shall occur in the following order unless the Optionholder elects in writing a different order (provided, however, that such election shall be subject to Company approval if made on or after the date that triggers the Payment or a portion thereof): (i) reduction of cash payments; (ii) cancellation of accelerated vesting of Options; and (iii) reduction of other benefits paid to the Optionholder. If acceleration of vesting of Options is to be reduced, such acceleration of vesting shall be cancelled in the reverse order of date of grant of Options (i.e., the earliest granted Option cancelled last) unless the Optionholder elects in writing a different order for cancellation.

(iii) For purposes of making the calculations required by this Section 11(e), the Accountant may make reasonable assumptions and approximations concerning applicable taxes and may rely on reasonable, good faith interpretations concerning the application of the Code and other applicable legal authority. The Company and the Optionholder shall furnish to the Accountant such information and documents as the Accountant may reasonably request in order to make such a determination. The Company shall bear all costs the Accountant may reasonably incur in connection with any calculations contemplated by this Section 11(e).

(iv) If, notwithstanding any reduction described above, the Internal Revenue Service (the “IRS”) determines that the Optionholder is liable for the Excise Tax as a result of the Payment, then the Optionholder shall be obligated to pay back to the Company, within thirty

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(30) days after a final IRS determination or, in the event that the Optionholder challenges the final IRS determination, a final judicial determination, a portion of the Payment (the “Repayment Amount”). The Repayment Amount with respect to the Payment shall be the smallest such amount, if any, as shall be required to be paid to the Company so that the Optionholder’s net after-tax proceeds with respect to the Payment (after taking into account the payment of the Excise Tax and all other applicable taxes imposed on the Payment) shall be maximized. The Repayment Amount with respect to the Payment shall be zero if a Repayment Amount of more than zero would not result in the Optionholder’s net after-tax proceeds with respect to the Payment being maximized. If the Excise Tax is not eliminated pursuant to this paragraph, the Optionholder shall pay the Excise Tax.

(v) Notwithstanding any other provision of this Section 11(e), if (i) there is a reduction in the Payment as described above, (ii) the IRS later determines that the Optionholder is liable for the Excise Tax, the payment of which would result in the maximization of the Optionholder’s net after-tax proceeds of the Payment (calculated as if the Payment had not previously been reduced), and (iii) the Optionholder pays the Excise Tax, then the Company shall pay or otherwise provide to the Optionholder that portion of the Payment that was reduced pursuant to this Section 11(e) contemporaneously or as soon as administratively possible after the Optionholder pays the Excise Tax so that the Optionholder’s net after-tax proceeds with respect to the Payment are maximized.

(vi) If the Optionholder either (i) brings any action to enforce rights pursuant to this Section 11(e), or (ii) defends any legal challenge to his or her rights under this Section 11(e), the Optionholder shall be entitled to recover attorneys’ fees and costs incurred in connection with such action, regardless of the outcome of such action; provided, however, that if such action is commenced by the Optionholder, the court finds that the action was brought in good faith.

(a) Amendment of Plan. Subject to the limitations, if any, of applicable law, the Board, at any time and from time to time, may amend the Plan. However, except as provided in Section 11(a) relating to Capitalization Adjustments, no amendment shall be effective unless approved by the stockholders of the Company to the extent stockholder approval is necessary to satisfy applicable law.

(b) Stockholder Approval. The Board, in its sole discretion, may submit any other amendment to the Plan for stockholder approval.

(c) No Impairment of Rights. Rights under any Option granted before amendment of the Plan shall not be impaired by any amendment of the Plan unless (i) the Company requests the consent of the affected Optionholder, and (ii) such Optionholder consents in writing.

(d) Amendment of Options. The Board, at any time and from time to time, may amend the terms of any one or more Options; provided, however, that the rights under any Option shall not be impaired by any such amendment unless (i) the Company requests the consent of the Optionholder, and (ii) the Optionholder consents in writing.

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(a) Plan Term. The Board may suspend or terminate the Plan at any time. No Options may be granted under the Plan while the Plan is suspended or after it is terminated.

(b) No Impairment of Rights. Suspension or termination of the Plan shall not impair rights and obligations under any Option granted while the Plan is in effect except with the written consent of the Optionholder.

The Plan shall become effective on the IPO Date, but no Option shall be exercised unless and until the Plan has been approved by the stockholders of the Company, which approval shall be within twelve (12) months before or after the date the Plan is adopted by the Board.

The law of the state of Delaware shall govern all questions concerning the construction, validity and interpretation of this Plan, without regard to such state’s conflict of laws rules.

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