X0609 4 2026-06-01 0001049502 MKS INC MKSI 0001842459 Henry David Philip false C/O MKS INC. 2 TECH DRIVE ANDOVER MA 01810 1 EVP, Global Str Mktg & GM, MSD 0 Common Stock 2026-06-01 4 S 0 6000 314.4305 D 10421.527 D This transaction was executed in multiple trades at prices ranging from $314.2425 to $314.955. 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 2026-06-02