X0306 4 2017-05-18 0 0001651235 Acacia Communications, Inc. ACIA 0001239366 CHUNG PETER Y C/O SUMMIT PARTNERS 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 0 0 Common Stock 2017-05-18 4 A 0 4446 0 A 1304573 I See Remarks. Represents restricted stock units awarded to Mr. Chung as compensation for services rendered as a director . Each restricted stock unit represents the right to receive one share of common stock upon vesting. The restricted stock units will vest entirely on May 18, 2018. Mr. Chung holds any restricted stock units for the benefit of Summit Partners, L.P., which he has empowered to determine when the underlying shares will be sold and which is entitled to the proceeds of any such sales. Consists of 987,039 shares held by Summit Partners Venture Capital Fund III-A, L.P., 299,157 shares held by Summit Partners Venture Capital Fund III-B, L.P., 12,860 shares held by Summit Investors I, LLC; 1,071 shares held by Summit Investors I (UK), L.P.and 4,446 restricted stock units held in the name of Peter Y. Chung, which are held for the benefit of Summit Partners, L.P. Summit Partners, L.P. is the managing member of Summit Partners VC III, LLC, which is the general partner of Summit Partners VC III, L.P., which is the general partner of each of Summit Partners Venture Capital Fund III-A, L.P. and Summit Partners Venture Capital Fund III-B, L.P. Summit Master Company, LLC is the managing member of Summit Investors Management, LLC, which is the manager of Summit Investors I, LLC, and the general partner of Summit Investors I (UK), L.P. Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated investment decisions, including dispositive power, to Summit Partners, L.P. and its investment committee responsible for voting and investment decisions with respect to the Issuer. Summit Partners, L.P., through a two-person investment committee responsible for voting and investment decisions with respect to the Issuer, currently comprised of Martin J. Mannion and Peter Y. Chung, has voting and dispositive power over the shares held by each of the entities listed above and Mr. Chung and therefore, may be deemed to beneficially own such shares. Mr. Chung is a member of Summit Master Company, LLC. Each of Summit Partners, L.P., the entities listed above, Mr. Mannion and Mr. Chung expressly disclaims beneficial ownership of such shares except to the extent of their pecuniary interest therein. Robin W. Devereux, Power of Attorney for Peter Y. Chung 2017-05-22