X0508 4 2026-02-20 0001049502 MKS INC MKSI 0001256715 COLELLA GERALD G C/O MKS INC. 2 TECH DRIVE ANDOVER MA 01810 1 0 Common Stock 2026-02-20 4 S 0 10000 252.8999 D 50017 I By The Gerald G. Colella 2019 Trust Common Stock 2026-02-24 4 S 0 10000 253.9675 D 40017 I By The Gerald G. Colella 2019 Trust Common Stock 8216.927 D This transaction was executed in multiple trades at prices ranging from $252.60 to $253.86. 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. This transaction was executed in multiple trades at prices ranging from $253.470 to $255.250. 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 2026-02-24