X0306 4 2015-04-02 0001049502 MKS INSTRUMENTS INC MKSI 0001600515 Quirk Brian Charles 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 Sr. VP, Global Operations Common Stock 2015-04-02 4 M 0 2469.407 33.74 A 8905.042 D Common Stock 2015-04-02 4 F 0 803 33.74 D 8102.042 D Restricted Stock Unit 2015-04-02 4 M 0 2469.407 0 D Common Stock 2469.407 11318.856 D This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person. 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 the first anniversary of the grant date, with the exception of RSUs granted on or after February 15, 2015, in which case, the annual vesting date shall be (i) February 15th or (ii) the next business day if February 15th is not a business day. /s/Renee M. Donlan POA 2015-04-03