X0306 4 2018-05-09 0001049502 MKS INSTRUMENTS INC MKSI 0001414656 Lee John Tseng-Chung 2 TECH DRIVE ANDOVER MA 01810 1 President & COO Restricted Stock Unit 2018-05-09 4 A 0 771.605 A Common Stock 771.605 19310.653 D Restricted Stock Unit 2018-05-09 4 A 0 1157.407 A Common Stock 1157.407 21109.491 D Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc. These RSUs vest in three equal annual installments commencing on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs are subject to the achievement of performance criteria determined in the first year of grant and thereafter vest in three equal annual installments beginning on February 15, 2019, 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 2018-05-10