X0306 4 2018-05-15 0 0001651235 Acacia Communications, Inc. ACIA 0001373044 MATRIX PARTNERS VIII L P C/O MATRIX PARTNERS 101 MAIN STREET, 17TH FLOOR CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2018-05-15 4 J 0 1000000 0.00 D 8646247 I By Matrix Partners VIII, L.P. Represents a pro-rata distribution, and not a purchase or sale, without additional consideration by Matrix Partners VIII, L.P. ("Matrix Partners VIII"), to its partners The shares are owned directly by Matrix Partners VIII. Matrix VIII US Management Co., L.L.C. (the "Matrix VIII US Management Co.") is the General Partner of Matrix Partners VIII and disclaims beneficial ownership of the shares owned by Matrix Partners VIII except to its proportionate pecuniary interest therein. Mr. Reiss, a member of the Board of Directors of the Issuer and a managing member of Matrix VIII US Management Co. has sole voting and dispositive power with respect to these shares. Mr. Reiss disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein. /s/ Stan Reiss, Managing Member of the Reporting Person 2018-05-17