SEC FORM 4

SEC FORM 4 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^*

Burke Kathleen Flaherty

(Last)

(First)

(Middle)

C/O MKS INC.

2 TECH DRIVE

(Street)

ANDOVER

01810

(City)

(State)

(Zip)

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, GC & Secretary

3. Date of Earliest Transaction (Month/Day/Year)
10/31/2025

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

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

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

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	10/31/2025		M		158	A	⁽¹⁾	51,232.509	D
Common Stock	10/31/2025		M		52	A	⁽¹⁾	51,284.509	D
Common Stock	10/31/2025		M		82	A	⁽¹⁾	51,366.509	D
Common Stock	10/31/2025		M		144	A	⁽¹⁾	51,510.509	D
Common Stock	10/31/2025		M		341	A	⁽¹⁾	51,851.509	D
Common Stock	10/31/2025		F⁽²⁾		777	D	$143.71	51,074.509	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Restricted Stock Unit	⁽¹⁾	10/31/2025		M			158	⁽³⁾	⁽³⁾	Common Stock	158	⁽¹⁾	17,617.737	D
Restricted Stock Unit	⁽¹⁾	10/31/2025		M			52	⁽⁴⁾	⁽⁴⁾	Common Stock	52	⁽¹⁾	17,565.737	D
Restricted Stock Unit	⁽¹⁾	10/31/2025		M			82	⁽³⁾	⁽³⁾	Common Stock	82	⁽¹⁾	17,483.737	D
Restricted Stock Unit	⁽¹⁾	10/31/2025		M			144	⁽⁴⁾	⁽⁴⁾	Common Stock	144	⁽¹⁾	17,339.737	D
Restricted Stock Unit	⁽¹⁾	10/31/2025		M			341	⁽⁵⁾	⁽⁵⁾	Common Stock	341	⁽¹⁾	16,998.737	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. Shares used to satisfy FICA taxes.

3. Portion of 2023 RSU Award accelerated to satisfy FICA taxes.

4. Portion of 2024 RSU Award accelerated to satisfy FICA taxes.

5. Portion of 2025 RSU Award accelerated to satisfy FICA taxes.

	/s/ M. Kathryn Rickards, attorney-in-fact	11/04/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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EVP, GC & Secretary Burke Kathleen Flaherty converted options into 777 shares and covered exercise/tax liability with 777 shares (SEC Form 4)