X0306 4 2015-02-25 0001049502 MKS INSTRUMENTS INC MKSI 0001414656 Lee John Tseng-Chung 2 TECH DRIVE ANDOVER MA 01810 1 Sr. VP, Business Units Common Stock 2015-02-25 4 M 0 2863.3 A 10258.678 D Common Stock 2015-02-25 4 M 0 2105 A 12363.678 D Common Stock 2015-02-25 4 F 0 1616 35.83 D 10747.678 D Restricted Stock Unit 2015-02-25 4 M 0 2863.3 D Common Stock 2863.3 23319.522 D Restricted Stock Unit 2015-02-25 4 M 0 2105 D Common Stock 2105 20814.68 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 grant and thereafter 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. 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 2015-02-26