X0306 4 2014-06-13 0001049502 MKS INSTRUMENTS INC MKSI 0001414656 Lee John Tseng-Chung 2 TECH DRIVE ANDOVER MA 01810 1 Sr. VP, Business Units Common Stock 2014-06-13 4 S 0 9128 29.546 D 0.051 D This transaction was executed in multiple trades at prices ranging from $29.41 to $29.71. 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 2014-06-16