X0508 4 2026-02-08 0001049502 MKS INC MKSI 0001414656 Lee John Tseng-Chung C/O MKS INC. 2 TECH DRIVE ANDOVER MA 01810 1 1 President & CEO 0 Restricted Stock Unit 2026-02-08 4 A 0 50971.84 A Common Stock 50971.84 139124.462 D Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Inc. These RSUs were subject to performance criteria, the achievement of which was determined on February 8, 2026, and thereafter vest in three equal annual installments beginning on February 15, 2026, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. /s/ M. Kathryn Rickards, attorney-in-fact 2026-02-09