X0306 4 2021-02-16 0001049502 MKS INSTRUMENTS INC MKSI 0001414656 Lee John Tseng-Chung C/O MKS INSTRUMENTS, INC. 2 TECH DRIVE, SUITE 201 ANDOVER MA 01810 1 1 President & CEO Common Stock 2021-02-16 4 M 0 1989.597 A 23698.251 D Common Stock 2021-02-16 4 M 0 1950.585 A 25648.836 D Common Stock 2021-02-16 4 M 0 263.037 A 25911.873 D Common Stock 2021-02-16 4 M 0 257.605 A 26169.478 D Common Stock 2021-02-16 4 M 0 3065.722 A 29235.2 D Common Stock 2021-02-16 4 M 0 2754.821 A 31990.021 D Common Stock 2021-02-16 4 M 0 7534 A 39524.021 D Common Stock 2021-02-16 4 M 0 4281 A 43805.021 D Common Stock 2021-02-16 4 F 0 9804 172.20 D 34001.021 D Restricted Stock Unit 2021-02-16 4 A 0 11811.847 A Common Stock 11811.847 63361.576 D Restricted Stock Unit 2021-02-16 4 M 0 1989.597 D Common Stock 1989.597 61371.979 D Restricted Stock Unit 2021-02-16 4 M 0 1950.585 D Common Stock 1950.585 59421.394 D Restricted Stock Unit 2021-02-16 4 M 0 263.037 D Common Stock 263.037 59158.357 D Restricted Stock Unit 2021-02-16 4 M 0 257.605 D Common Stock 257.605 58900.752 D Restricted Stock Unit 2021-02-16 4 M 0 3065.722 D Common Stock 3065.722 55835.03 D Restricted Stock Unit 2021-02-16 4 M 0 2754.821 D Common Stock 2754.821 53080.209 D Restricted Stock Unit 2021-02-16 4 M 0 7534 D Common Stock 7534 45546.209 D Restricted Stock Unit 2021-02-16 4 M 0 4281 D Common Stock 4281 41265.209 D Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Instruments, Inc. This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person. These RSUs vest in three equal annual installments commencing on February 15, 2022, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs were subject to performance criteria, the achievement of which was determined on January 28, 2019, and thereafter vest in three equal annual installments beginning on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs vest in three equal annual installments commencing on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs were subject to performance criteria, the achievement of which was determined on January 27, 2020, and thereafter vest in three equal installments beginning on February 15, 2020, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs vest in three equal annual installments commencing on February 15, 2020, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs were subject to performance criteria, the achievement of which was determined on January 25, 2021, and thereafter vest in three equal annual installments beginning on February 15, 2021, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. These RSUs vest in three equal annual installments commencing on February 15, 2021, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day. /s/ M. Kathryn Rickards, attorney-in-fact 2021-02-17