MKS Inc (MKSI) EVP Williams logs RSU vesting and tax-share withholding

Rhea-AI Filing Summary

MKS Inc EVP & GM, PSD John Edward Williams reported routine equity compensation activity involving restricted stock units (RSUs). On April 17, 2026, RSUs representing 1,740.714 shares of common stock were converted into common shares, reflecting the vesting of previously granted awards.

To cover tax withholding obligations from this RSU vesting, 825.969 common shares were withheld by MKS Inc, which the company notes does not represent a discretionary trade by Williams. Following these transactions, he directly holds 5,380.813 shares of MKS Inc common stock.

Insider Trade Summary

1,740.714 shares exercised/converted

Mixed 3 txns

Insider Williams John Edward

Role EVP & GM, PSD

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit	1,740.714	$0.00	--
Exercise	Common Stock	1,740.714	$0.00	--
Tax Withholding	Common Stock	825.969	$269.89	$223K

Holdings After Transaction: Restricted Stock Unit — 6,812.003 shares (Direct, null); Common Stock — 5,380.813 shares (Direct, null)

Footnotes (1)

1. Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Inc. These shares were withheld by MKS Inc. to satisfy the tax withholding obligations triggered by the vesting of RSUs and do not represent a discretionary trade by the reporting person. These RSUs vest in two equal annual installments commencing on April 17, 2025, provided that if, in any vesting year, April 17th is not a business day, such vesting shall occur on the next business day.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Williams John Edward

(Last) (First) (Middle)

C/O MKS INC.

2 TECH DRIVE

(Street)

ANDOVER MASSACHUSETTS 01810

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MKS INC [ MKSI ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP & GM, PSD

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/17/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	04/17/2026		M		1,740.714	A	(1)	5,380.813	D
Common Stock	04/17/2026		F(2)		825.969	D	$269.89	4,554.844	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Unit	(1)	04/17/2026		M			1,740.714	(3)	(3)	Common Stock	1,740.714	(1)	6,812.003	D

Explanation of Responses:

1. Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Inc.

2. These shares were withheld by MKS Inc. to satisfy the tax withholding obligations triggered by the vesting of RSUs and do not represent a discretionary trade by the reporting person.

3. These RSUs vest in two equal annual installments commencing on April 17, 2025, provided that if, in any vesting year, April 17th is not a business day, such vesting shall occur on the next business day.

	/s/ James Kruger, attorney-in-fact	04/20/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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* Form 4: SEC 1474 (03-26)