X0306 4 2018-04-30 0 0001333835 Casa Systems Inc CASA 0000830588 SUMMIT PARTNERS L P 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 1 1 Manager of GP of 10% owner 0001627278 SUMMIT MASTER COMPANY, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 0 0 1 1 Manager of Manager of 10% owne 0001486418 Summit Partners PE VII, L.P. 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 1 1 GP of 10% owner. 0001486419 Summit Partners PE VII, LLC 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 1 1 GP of GP of 10% owner 0001507545 Summit Investors Management, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 0 0 1 1 Manager and GP of 10% Owner 0001486421 Summit Partners Private Equity Fund VII-A, L.P. 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 1 0 0001385242 Summit Partners Private Equity Fund VII B L P 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 1 0 0001435565 Summit Investors I, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 0 0 1 0 0001494616 Summit Investors I (UK), L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 0 0 1 0 Common Stock 2018-04-30 4 S 0 4717520 25 D 34124480 I See Footnotes Consists of 2,940,250 shares of common stock sold by Summit Partners Private Equity Fund VII-A, L.P., 1,765,961 shares of common stock sold by Summit Partners Private Equity Fund VII-B, L.P., 10,037 shares of common stock sold by Summit Investors I, LLC and 1,272 shares of common stock sold by Summit Investors I (UK), L.P. Of the shares sold by the reporting persons mentioned in footnote (1), the sale of 250,000 shares is matchable under Section 16(b) of the Securities Exchange Act of 1934, as amended, with the purchase of 250,000 shares on December 19, 2017 at $13.0 per share. The reporting persons mentioned in footnote (1) have paid to the issuer an aggregate of $2,721,875.00, representing the full amount of the profit realized in connection with the short-swing transaction, less transaction costs. Consists of 21,268,476 shares of common stock held by Summit Partners Private Equity Fund VII-A, L.P., 12,774,194 shares of common stock held by Summit Partners Private Equity Fund VII-B, L.P., 72,605 shares of common stock issued held by Summit Investors I, LLC and 9,205 shares of common stock held by Summit Investors I (UK), L.P. Summit Partners, L.P. is the managing member of Summit Partners PE VII, LLC, which is the general partner of Summit Partners PE VII, L.P., which is the general partner of each of Summit Partners Private Equity Fund VII-A, L.P. and Summit Partners Private Equity Fund VII-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 voting and 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 three-person investment committee responsible for voting and investment decisions with respect to the Issuer, currently comprised of Peter Y. Chung, Bruce R. Evans and Martin J. Mannion, has voting and dispositive power over the shares held by each of these entities and therefore may be deemed to beneficially own such shares. Each of the Summit entities and persons mentioned in this footnote disclaims beneficial ownership of the shares, except for those shares held of record by such entity, and except to the extent of their pecuniary interest therein. Summit Partners, L.P., by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member 2018-04-30 Summit Master Company, LLC, by Robin W. Devereux, Member 2018-04-30 Summit Partners PE VII, L.P., by Summit Partners PE VII, LLC, its GP, by Summit Partners, L.P., its Manager, Summit Master Company, LLC, by Robin W. Devereux, Member 2018-04-30 Summit Partners PE VII, LLC, by Summit Partners, L.P., its Manager, Summit Master Company, LLC, by Robin W. Devereux, Membe 2018-04-30 Summit Investors Management, LLC, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-04-30 Summit Partners Private Equity Fund VII-A, L.P., by Summit Partners PE VII, L.P., its GP, by Summit Partners PE VII, LLC, its GP, by Summit Partners, L.P., its Managing Member, Summit Master Company, LLC, by Robin W. Devereux, Member 2018-04-30 Summit Partners Private Equity Fund VII-B, L.P., by Summit Partners PE VII, L.P., its GP, by Summit Partners PE VII, LLC, its GP, by Summit Partners, L.P., its Managing Member, Summit Master Company, LLC, by Robin W. Devereux, Member 2018-04-30 Summit Investors I, LLC, by Summit Investors Management, LLC, its Manager, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-04-30 Summit Investors I (UK), L.P., by Summit Investors Management, LLC, its General Partner, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-04-30