X0306 4 2021-11-04 0001049502 MKS INSTRUMENTS INC MKSI 0001256715 COLELLA GERARD G C/O MKS INSTRUMENTS, INC. 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 Common Stock 2021-11-04 4 S 0 3000 155.1625 D 97000 I By The Gerald G. Colella Living Trust Common Stock 1148.636 D This transaction was executed in multiple trades at prices ranging from $153.03 to $156.95. 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/ M. Kathryn Rickards, attorney-in-fact 2021-11-05