Description of Securities

Exhibit 4.5

DESCRIPTION OF REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934

As of December 31, 2021, the end of the period covered by this Annual Report on Form 10-K, Mount Rainer Acquisition Corp. (the “Company,” “we,” “us,” or “our”) had three classes of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”): the Company’s units, common stock, and warrants.

The following description of the Company’s capital stock and provisions of the Company’s amended and restated certificate of incorporation, bylaws and the Delaware General Corporation Law are summaries and are qualified in their entirety by reference to the Company’s amended and restated certificate of incorporation and bylaws and the text of the Delaware General Corporation Law. Copies of these documents have been filed with the SEC as exhibits to the Annual Report on Form 10-K to which this description has been filed as an exhibit.

General

Our amended and restated certificate of incorporation authorizes the issuance of 50,000,000 shares of common stock, par value $0.0001. As of the date of this Annual Report on Form 10-K, 22,158,700 shares of common stock are issued and outstanding and no preferred shares are issued or outstanding. The following description summarizes all of the material terms of our securities. Because it is only a summary, it may not contain all the information that is important to you. For a complete description you should refer to our amended and restated certificate of incorporation and bylaws, which are filed as exhibits to this Annual Report on Form 10-K.

Units

Each unit consists of one share of common stock and one warrant. Each warrant entitles the holder thereof to purchase three-fourths (3/4) of a share of common stock at a price of $11.50 per whole share, subject to adjustment. Each warrant will become exercisable on the later of one year after the closing of the IPO, or October 7, 2022, or 30 days after the completion of an initial business combination, and will expire five years after the completion of an initial business combination, or earlier upon redemption. Pursuant to the warrant agreement, a warrantholder may exercise its warrants only for a whole number of shares. This means that only an even number of public warrants may be exercised at any given time by a warrantholder. For example, if a warrant holder holds one public warrant to purchase three-fourths (3/4) of one share, such warrant shall not be exercisable. If a warrantholder holds four public warrants, such public warrants will be exercisable for three shares of common stock.

The shares of common stock and warrants comprising the units became separately traded on January 3, 2022.

Common Stock

Our holders of record of our common stock are entitled to one vote for each share held on all matters to be voted on by stockholders. In connection with any vote held to approve our initial business combination, our insiders, officers and directors, have agreed to vote their respective shares of common stock owned by them immediately prior to the IPO, including both the insider shares and any shares acquired in the IPO or following the IPO in the open market, in favor of the proposed business combination.

We will consummate our initial business combination only if public stockholders do not exercise conversion rights in an amount that would cause our net tangible assets to be less than $5,000,001 and a majority of the outstanding shares of common stock voted are voted in favor of the business combination.

Pursuant to our amended and restated certificate of incorporation, if we do not consummate our initial business combination within 15 months from the closing of the IPO, we will (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than five business days thereafter, redeem 100% of the outstanding public shares, which redemption will completely extinguish public stockholders’ rights as stockholders (including the right to receive further liquidation distributions, if any), subject to applicable law, and (iii) as promptly

as reasonably possible following such redemption, subject to the approval of our remaining stockholders and our board of directors, dissolve and liquidate, subject (in the case of (ii) and (iii) above) to our obligations under Delaware law to provide for claims of creditors and the requirements of other applicable law. Our insiders have agreed to waive their rights to share in any distribution with respect to their insider shares.

Our stockholders have no conversion, preemptive or other subscription rights and there are no sinking fund or redemption provisions applicable to the shares of common stock, except that public stockholders have the right to sell their shares to us in any tender offer or have their shares of common stock converted to cash equal to their pro rata share of the trust account if they vote on the proposed business combination and the business combination is completed.

If we hold a stockholder vote to amend any provisions of our certificate of incorporation relating to stockholder’s rights or pre-business combination activity (including the substance or timing within which we have to complete a business combination), we will provide our public stockholders with the opportunity to redeem their shares of common stock upon approval of any such amendment at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the trust account, including interest earned on the funds held in the trust account and not previously released to us to pay our franchise and income taxes, divided by the number of then outstanding public shares, in connection with any such vote. In either of such events, converting stockholders would be paid their pro rata portion of the trust account promptly following consummation of the business combination or the approval of the amendment to the certificate of incorporation. If the business combination is not consummated or the amendment is not approved, stockholders will not be paid such amounts.

Warrants

Each warrant will entitle the registered holder to purchase three-fourths (3/4) of a share of common stock at a price of $11.50 per whole share, subject to adjustment as discussed below, upon the later of: (i) one year after the date that the closing of the IPO, or October 7, 2022; and (ii) 30 days following the consummation by us of a business combination and terminating on the five-year anniversary of the completion of the business combination.

Pursuant to the warrant agreement, a warrantholder may exercise its warrants only for a whole number of shares. This means that only warrants in increments of four may be exercised at any given time by a warrantholder. However, no warrants will be exercisable for cash unless we have an effective and current registration statement covering the shares of common stock issuable upon exercise of the warrants and a current prospectus relating to such shares of common stock. Notwithstanding the foregoing, if a registration statement covering the shares of common stock issuable upon exercise of the warrants is not effective within 120 days from the closing of our initial business combination, warrant holders may, until such time as there is an effective registration statement and during any period when we shall have failed to maintain an effective registration statement, exercise warrants on a cashless basis pursuant to an available exemption from registration under the Securities Act. The warrants will expire five years from the closing of our initial business combination at 5:00 p.m., New York City time.

We may call the outstanding warrants for redemption (including any warrants already issued upon exercise of the unit purchase option), in whole and not in part, at a price of $0.01 per warrant:

The right to exercise will be forfeited unless the warrants are exercised prior to the date specified in the notice of redemption. On and after the redemption date, a record holder of a warrant will have no further rights except to receive the redemption price for such holder’s warrant upon surrender of such warrant.

The redemption criteria for our warrants have been established at a price which is intended to provide warrant holders a reasonable premium to the initial exercise price and provide a sufficient differential between the then-prevailing share price and the warrant exercise price so that if the share price declines as a result of our redemption call, the redemption will not cause the share price to drop below the exercise price of the warrants.

If we call the warrants for redemption as described above, our management will have the option to require all holders that wish to exercise warrants to do so on a “cashless basis.” In such event, each holder would pay the exercise price by surrendering the warrants for that number of shares of common stock equal to the quotient obtained by dividing (x) the product of the number of shares of common stock underlying the warrants, multiplied by the difference between the exercise price of the warrants and the “fair market value” (defined below) by (y) the fair market value. The “fair market value” shall mean the average reported last sale price of our common stock for the 20 trading days ending on the third trading day prior to the date on which the notice of redemption is sent to the holders of warrants. Whether we will exercise our option to require all holders to exercise their warrants on a “cashless basis” will depend on a variety of factors including the price of our common shares at the time the warrants are called for redemption, our cash needs at such time and concerns regarding dilutive share issuances.

The warrants will be issued in registered form under a warrant agreement between American Stock Transfer & Trust Company, LLC, as warrant agent, and us. The warrant agreement provides that the terms of the warrants may be amended without the consent of any holder to cure any ambiguity or correct any defective provision, but requires the approval, by written consent or vote, of the holders of a majority of the then outstanding warrants in order to make any change that adversely affects the interests of the registered holders.

The exercise price and number of shares of common stock issuable on exercise of the warrants may be adjusted in certain circumstances including in the event of a share dividend, extraordinary dividend or our recapitalization, reorganization, merger or consolidation. However, except as described below, the warrants will not be adjusted for issuances of shares of common stock at a price below their respective exercise prices.

If (x) we issue additional shares of common stock or equity-linked securities for capital raising purposes in connection with the closing of our initial business combination at an issue price or effective issue price of less than $9.20 per share of common stock (with such issue price or effective issue price to be determined in good faith by our board of directors, and in the case of any such issuance to our sponsor, initial stockholders or their affiliates, without taking into account any founders’ shares held by them prior to such issuance), (y) the aggregate gross proceeds from such issuances represent more than 60% of the total equity proceeds, and interest thereon, available for the funding of our initial business combination on the date of the consummation of our initial business combination (net of redemptions), and (z) the Market Value is below $9.20 per share, the exercise price of the warrants will be adjusted (to the nearest cent) to be equal to 115% of the greater of (i) the Market Value or (ii) the price at which we issue the additional shares of common stock or equity-linked securities and the $18.00 per share redemption trigger price described above will be adjusted (to the nearest cent) to be equal to 180% of the Market Value. The warrants may be exercised upon surrender of the warrant certificate on or prior to the expiration date at the offices of the warrant agent, with the exercise form on the reverse side of the warrant certificate completed and executed as indicated, accompanied by full payment of the exercise price, by certified or official bank check payable to us, for the number of warrants being exercised. The warrant holders do not have the rights or privileges of holders of shares of common stock and any voting rights until they exercise their warrants and receive shares of common stock. After the issuance of shares of common stock upon exercise of the warrants, each holder will be entitled to one vote for each share held of record on all matters to be voted on by stockholders.

Except as described above, no warrants will be exercisable for cash and we will not be obligated to issue shares of common stock unless at the time a holder seeks to exercise such warrant, a prospectus relating to the shares of common stock issuable upon exercise of the warrants is current and the shares of common stock have been registered or qualified or deemed to be exempt under the securities laws of the state of residence of the holder of the warrants. Under the terms of the warrant agreement, we have agreed to use our best efforts to meet these conditions and to maintain a current prospectus relating to the shares of common stock issuable upon exercise of the warrants until the

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expiration of the warrants. However, we cannot assure you that we will be able to do so and, if we do not maintain a current prospectus relating to the shares of common stock issuable upon exercise of the warrants, holders will be unable to exercise their warrants and we will not be required to settle any such warrant exercise. If the prospectus relating to the shares of common stock issuable upon the exercise of the warrants is not current or if the common stock is not qualified or exempt from qualification in the jurisdictions in which the holders of the warrants reside, we will not be required to net cash settle or cash settle the warrant exercise, the warrants may have no value, the market for the warrants may be limited and the warrants may expire worthless.

Warrant holders may elect to be subject to a restriction on the exercise of their warrants such that an electing warrant holder would not be able to exercise their warrants to the extent that, after giving effect to such exercise, such holder would beneficially own in excess of 9.9% of the shares of common stock outstanding.

No fractional shares will be issued upon exercise of the warrants. If, upon exercise of the warrants, a holder would be entitled to receive a fractional interest in a share, we will, upon exercise, round down to the nearest whole number of shares of common stock to be issued to the warrant holder.

We have agreed that, subject to applicable law, any action, proceeding or claim against us arising out of or relating in any way to the warrant agreement will be brought and enforced in the courts of the State of New York or the United States District Court for the Southern District of New York, and we irrevocably submit to such jurisdiction, which jurisdiction will be the exclusive forum for any such action, proceeding or claim. This provision applies to claims under the Securities Act but does not apply to claims under the Exchange Act or any claim for which the federal district courts of the United States of America are the sole and exclusive forum. We note that there is uncertainty as to whether a court would enforce this provision and that investors cannot waive compliance with the federal securities laws and the rules and regulations thereunder. Section 22 of the Securities Act creates concurrent jurisdiction for state and federal courts over all suits brought to enforce any duty or liability created by the Securities Act or the rules and regulations thereunder.

Dividends

We have not paid any cash dividends on our shares of common stock to date and do not intend to pay cash dividends prior to the completion of a business combination. The payment of cash dividends in the future will be dependent upon our revenues and earnings, if any, capital requirements and general financial condition subsequent to completion of a business combination. The payment of any dividends subsequent to a business combination will be within the discretion of our then board of directors. It is the present intention of our board of directors to retain all earnings, if any, for use in our business operations and, accordingly, our board does not anticipate declaring any dividends in the foreseeable future.

Our Transfer Agent and Warrant Agent

The transfer agent for our shares of common stock and warrant agent for our warrants is American Stock Transfer & Trust Company, LLC, 6201 15th Avenue, Brooklyn, NY 11219.

Certain Anti-Takeover Provisions of Delaware Law and our Amended and Restated Certificate of Incorporation and Bylaws

We are subject to the provisions of Section 203 of the DGCL regulating corporate takeovers. This statute prevents certain Delaware corporations, under certain circumstances, from engaging in a “business combination” with:

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A “business combination” includes a merger or sale of more than 10% of our assets. However, the above provisions of Section 203 do not apply if:

Special meeting of stockholders

Our bylaws provide that special meetings of our stockholders may be called by resolution of the Board of Directors, or by the Chief Executive Officer, or by the holders of not less than one-quarter of all of the shares entitled to vote at the meeting.

Advance notice requirements for stockholder proposals and director nominations

Our bylaws provide that stockholders seeking to bring business before our annual meeting of stockholders, or to nominate candidates for election as directors at our annual meeting of stockholders must provide timely notice of their intent in writing. To be timely, a stockholder’s notice will need to be delivered to our principal executive offices not later than the close of business on the 90th day nor earlier than the opening of business on the 120th day prior to the scheduled date of the annual meeting of stockholders. Our bylaws also specify certain requirements as to the form and content of a stockholders’ meeting. These provisions may preclude our stockholders from bringing matters before our annual meeting of stockholders or from making nominations for directors at our annual meeting of stockholders

Authorized but unissued shares

Our authorized but unissued common stock are available for future issuances without stockholder approval and could be utilized for a variety of corporate purposes, including future offerings to raise additional capital, acquisitions and employee benefit plans. The existence of authorized but unissued and unreserved common stock could render more difficult or discourage an attempt to obtain control of us by means of a proxy contest, tender offer, merger or otherwise.

Exclusive forum for certain lawsuits

Our amended and restated certificate of incorporation provide that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware shall, to the fullest extent permitted by law, be the sole and exclusive forum for any (1) derivative action or proceeding brought on behalf of our company, (2) action asserting a claim of breach of a fiduciary duty owed by any director, officer, employee or agent of our company to our company or our stockholders, or any claim for aiding and abetting any such alleged breach, (3) action asserting a claim against our company or any director or officer of our company arising pursuant to any provision of the DGCL or our amended and restated certificate of incorporation or our bylaws, or (4) action asserting a claim against us or any director or officer of our company governed by the internal affairs doctrine except for, as to each of (1) through (4) above, any claim (A) as to which the Court of Chancery determines that there is an indispensable party not subject to the jurisdiction of the Court of Chancery (and the indispensable party does not consent to the personal jurisdiction of the Court of Chancery within ten days following such determination), (B) which is vested in the exclusive jurisdiction of a court or forum other than the Court of Chancery, or (C) arising under the federal securities laws, including the Securities Act as to which the Court of Chancery and the federal district court for the District of Delaware shall concurrently be the sole and exclusive forums. Notwithstanding the foregoing, the inclusion of such provision in our amended and restated certificate of incorporation will not be deemed to be a waiver by our stockholders of our

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obligation to comply with federal securities laws, rules and regulations, and the provisions of this paragraph will not apply to suits brought to enforce any liability or duty created by the Exchange Act or any other claim for which the federal district courts of the United States of America shall be the sole and exclusive forum. Although we believe this provision benefits us by providing increased consistency in the application of Delaware law in the types of lawsuits to which it applies, the provision may have the effect of discouraging lawsuits against our directors and officers. Furthermore, the enforceability of choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that a court could find these types of provisions to be inapplicable or unenforceable.