X0306 4 2017-02-10 0001049502 MKS INSTRUMENTS INC MKSI 0001600515 Quirk Brian Charles 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 Sr. VP, Global Operations Common Stock 2017-02-10 4 M 0 3013.256 A 12222.774 D Common Stock 2017-02-10 4 M 0 2009.171 A 14231.945 D Common Stock 2017-02-10 4 F 0 1690 66.95 D 12541.945 D Restricted Stock Unit 2017-02-10 4 M 0 3013.256 D Common Stock 3013.256 17628.434 D Restricted Stock Unit 2017-02-10 4 M 0 2009.171 D Common Stock 2009.171 10018.154 D Restricted Stock Unit 2017-02-13 4 J 0 1294.401 D Common Stock 1294.401 16334.033 D Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc. This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person. These RSUs are subject to the achievement of performance criteria determined in the first year of the grant and thereafter vest in equal annual installments over three years. The RSUs vest in equal annual installments over three years from the respective original grant date. 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, 2017, 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 2017-02-11