X0306 4 2014-07-24 0001049502 MKS INSTRUMENTS INC MKSI 0001192439 BAGSHAW SETH H C/O MKS 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 Vice President, CFO, Treasurer Common Stock 2014-07-24 4 S 0 5000 32.615 D 31800.94 D This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person. This transaction was executed in multiple trades at prices ranging from $32.58 to $32.74. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide, upon request, the full information regarding the number of shares and prices at which the transaction was effected. /s/Renee M. Donlan POA 2014-07-25