MKS Inc. (MKSI) CEO sells 30,000 shares in open-market trades

Rhea-AI Filing Summary

MKS Inc. President & CEO Lee John Tseng-Chung reported selling a total of 30,000 shares of common stock in open-market transactions. The sales occurred on February 20, 2026 at weighted average prices around $256–$260 per share across multiple trade executions.

Individual reported trades covered 13,310 shares at $256.0538, 12,812 shares at $256.9313, 1,988 shares at $257.8084, and 1,890 shares at $259.7032. After these transactions, he directly owns about 154,696.1077 shares of MKS Inc. common stock.

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^*

Lee John Tseng-Chung

(Last) (First) (Middle)

C/O MKS INC.

2 TECH DRIVE

(Street)

ANDOVER MA 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)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President & CEO

3. Date of Earliest Transaction (Month/Day/Year)
02/20/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	02/20/2026		S		13,310	D	$256.0538(1)	171,386.1077	D
Common Stock	02/20/2026		S		12,812	D	$256.9313(2)	158,574.1077	D
Common Stock	02/20/2026		S		1,988	D	$257.8084(3)	156,586.1077	D
Common Stock	02/20/2026		S		1,890	D	$259.7032(4)	154,696.1077	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

Explanation of Responses:

1. This transaction was executed in multiple trades at prices ranging from $255.425 to $256.415. 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.

2. This transaction was executed in multiple trades at prices ranging from $256.4275 to $257.275. 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.

3. This transaction was executed in multiple trades at prices ranging from $257.445 to $258.320. 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.

4. This transaction was executed in multiple trades at prices ranging from $259.170 to $259.920. 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	02/23/2026
	** 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.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did MKS Inc (MKSI) report on this Form 4?

MKS Inc. reported that President & CEO Lee John Tseng-Chung sold 30,000 shares of common stock in a series of open-market transactions on February 20, 2026, as disclosed in a Form 4 insider trading report.

How many MKS Inc (MKSI) shares did the CEO sell and at what prices?

The CEO sold a total of 30,000 MKS Inc. common shares. Reported weighted average sale prices were approximately $256.05, $256.93, $257.81, and $259.70 per share, with each transaction executed through multiple trades within stated price ranges.

On what date did Lee John Tseng-Chung sell MKS Inc (MKSI) stock?

All reported stock sales by President & CEO Lee John Tseng-Chung occurred on February 20, 2026. The Form 4 shows four separate open-market sale transactions in MKS Inc. common stock, each with its own share amount and weighted average sale price.

How many MKS Inc (MKSI) shares does the CEO own after these sales?

Following the reported transactions, President & CEO Lee John Tseng-Chung directly owns about 154,696.1077 shares of MKS Inc. common stock. The Form 4 lists this direct ownership figure after the final open-market sale on February 20, 2026.

Were the MKS Inc (MKSI) CEO’s stock sales single trades or multiple executions?

Each reported sale was executed through multiple trades within specified price ranges. The Form 4 notes that the prices shown are weighted average sale prices, and detailed trade-by-trade information is available from the reporting person upon request.