MKS Inc (NASDAQ: MKSI) CEO sells 10,000 shares under 10b5-1 plan

Rhea-AI Filing Summary

MKS INC executive John Tseng-Chung Lee, President & CEO, reported selling 10,000 shares of Common Stock on 2026-08-14 at $302.01 per share in an open-market or private transaction. Following the sale, he directly holds 134,776.2667 shares. The sale was executed under a Rule 10b5-1 trading plan adopted on February 20, 2026.

Insider Trade Summary 10b5-1

Net Seller: 10,000 shares

Net Sell 1 txn

Insider Lee John Tseng-Chung

Role President & CEO

Sold 10,000 shs ($3.02M)

Type	Security	Shares	Price	Value
Sale	Common Stock F1	10,000	$302.01	$3.02M

Holdings After Transaction: Common Stock — 134,776.2667 shares (Direct)

Footnotes (1)

1. F1. This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2026.

Key Figures

Shares sold: 10,000 shares Sale price per share: $302.01 per share Shares held after transaction: 134,776.2667 shares +1 more

4 metrics

Shares sold 10,000 shares Common Stock sale on 2026-08-14

Sale price per share $302.01 per share Price for 10,000-share Common Stock sale

Shares held after transaction 134,776.2667 shares Direct ownership following 2026-08-14 sale

Net shares sold 10,000 shares transactionSummary netBuySellShares (net-sell)

Key Terms

Rule 10b5-1 trading plan, open market or private transaction, Common Stock

3 terms

Rule 10b5-1 trading plan regulatory

"This transaction was effected pursuant to a Rule 10b5-1 trading plan"

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

open market or private transaction financial

"transaction_code_description: Sale in open market or private transaction"

Common Stock financial

"security_title: Common Stock"

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

FAQ

What insider transaction did MKSI President & CEO John Tseng-Chung Lee report?

John Tseng-Chung Lee reported a sale of 10,000 shares of MKS INC (MKSI) Common Stock. The transaction occurred on 2026-08-14 at a price of $302.01 per share in an open-market or private transaction.

How many MKSI shares does John Tseng-Chung Lee hold after this Form 4 transaction?

After the reported sale, John Tseng-Chung Lee directly holds 134,776.2667 MKSI shares. This figure reflects his direct ownership position immediately following the 10,000-share disposition disclosed in the Form 4 filing.

At what price did the MKSI insider sell shares in the latest Form 4 filing?

The MKSI insider sale was executed at $302.01 per share. The Form 4 indicates a 10,000-share sale of Common Stock at this per-share price in an open-market or private transaction on 2026-08-14.

Was the recent MKSI insider sale by John Tseng-Chung Lee under a Rule 10b5-1 plan?

Yes. The reported transaction was effected pursuant to a Rule 10b5-1 trading plan. A footnote states the plan was adopted on February 20, 2026, indicating the sale followed a pre-arranged trading schedule.

How many MKSI shares were sold in total in this Form 4 filing?

The Form 4 reports total sales of 10,000 MKSI shares. Transaction summary data show a sellCount of 1 and sellShares of 10,000, with net buy/sell activity described as net-sell of 10,000 shares for the period covered.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 08/17/2026 - 10:12 AM Accepted by SEC EDGAR 08/17/2026 - 10:11 AM Learn about SEC filing dates

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

X

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 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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/14/2026

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	08/14/2026		S(1)		10,000	D	$302.01	134,776.2667	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 effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2026.

	/s/ M. Kathryn Rickards, attorney-in-fact	08/17/2026
	** 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.
* Form 4: SEC 1474 (03-26)