X0306 4 2018-02-12 0001049502 MKS INSTRUMENTS INC MKSI 0001600505 Abrams John R 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 Sr. VP, Global Sales & Service Restricted Stock Unit 2018-02-12 4 J 0 1285.081 D Common Stock 1285.081 12324.908 D Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc. This transaction reflects the forfeiture of RSUs due to performance criteria. 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, 2018, 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 2018-02-12