Promotion Letter dated December 26, 2017, executed by Russell Klein

Promotion Grant. An option to purchase 150,581 shares of the Company’s common stock at a price per share equal to the fair market value of the common stock on the date upon which the Board of Directors approves the option grant (the “Promotion Grant”). We will recommend to the Company’s Board of Directors that 25% of the shares subject to the Promotion Grant vest on the first anniversary of the effective date above and in equal monthly installments thereafter over a total vesting period of four (4) years, provided you remain an employee of the Company.

Liquidity Event Grant. An option to purchase 150,581 shares of the Company’s common stock at a price per share equal to the fair market value of the common stock on the date upon which the Board of Directors approves the option grant (the “Liquidity Event Grant”). We will recommend to the Company’s Board of Directors that 100% of the shares subject to the Liquidity Event Grant vest immediately prior to and conditioned upon the closing of a Qualifying Liquidity Event that occurs before December 31, 2019. A “Qualifying Liquidity Event” means one of the following transactions that values the Company at or in excess of $1 billion immediately prior to the transaction: (i) a Change in Control, as that term is defined in the 2013 Stock Plan, or (ii) a Qualified IPO, as that term is currently defined in the Company’s certificate of incorporation.