MKSI insider plans sale of 10,000 common shares

MKSI reporting person John Tseng-Chung Lee filed to sell 10,000 shares of common stock through Fidelity Brokerage Services on NASDAQ, with an approximate aggregate market value of $3,020,100.00, expected on or about 08/14/2026.

Rhea-AI Filing Summary

MKSI reporting person John Tseng-Chung Lee filed to sell 10,000 shares of common stock through Fidelity Brokerage Services on NASDAQ, with an approximate aggregate market value of $3,020,100.00, expected on or about 08/14/2026. The notice also lists a prior sale of 10,000 shares on 05/22/2026 for about $3,154,800.00, and notes the shares originated from restricted stock vesting events in 2021 and 2022 classified as compensation.

Key Figures

Planned shares to be sold: 10,000 shares Planned aggregate market value: $3,020,100.00 Prior 3‑month sale shares: 10,000 shares +3 more

6 metrics

Planned shares to be sold 10,000 shares Common stock to be sold through Fidelity Brokerage Services on or about 08/14/2026

Planned aggregate market value $3,020,100.00 Approximate aggregate market value of the 10,000 common shares to be sold

Prior 3‑month sale shares 10,000 shares Common shares sold on 05/22/2026 during the past 3 months

Prior 3‑month sale value $3,154,800.00 Approximate aggregate market value of shares sold on 05/22/2026

Restricted stock vesting 2021 9,633 shares Common stock from restricted stock vesting on 02/15/2021 classified as compensation

Restricted stock vesting 2022 367 shares Common stock from restricted stock vesting on 02/15/2022 classified as compensation

Key Terms

Restricted Stock Vesting, Compensation, Securities To Be Sold, Securities Sold During The Past 3 Months

4 terms

Restricted Stock Vesting financial

"Common | 02/15/2021 | Restricted Stock Vesting | Issuer"

Restricted stock vesting is the timetable and conditions under which shares granted to employees or insiders become fully owned and can be sold, typically requiring continued work or meeting performance goals. It matters to investors because large blocks of shares can become tradable at once, which can change share supply and price, and because vesting aligns insiders’ incentives with the company’s long‑term performance—think of it like a timed unlock that both rewards and locks in key people.

Compensation financial

"02/15/2021 | Compensation Common | 02/15/2022 | Compensation"

Securities To Be Sold regulatory

"144: Securities To Be Sold"

Securities Sold During The Past 3 Months regulatory

"144: Securities Sold During The Past 3 Months"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stock sale is disclosed for MKSI in this Form 144 filing?

The filing discloses that John Tseng-Chung Lee plans to sell 10,000 common shares of MKSI through Fidelity Brokerage Services on NASDAQ, with an approximate aggregate market value of $3,020,100.00, expected on or about 08/14/2026.

What is the recent sale history for the MKSI insider in this Form 144?

The document notes a prior sale of 10,000 MKSI common shares on 05/22/2026 with an approximate aggregate market value of $3,154,800.00. This provides recent trading context for the same reporting person’s holdings.

What is the planned sale value of MKSI shares under this Form 144?

The planned sale covers 10,000 MKSI common shares with an approximate aggregate market value of $3,020,100.00. This value reflects the estimate reported for the Rule 144 transaction via Fidelity Brokerage Services on NASDAQ.

How were the MKSI shares being sold originally acquired by the insider?

The filing indicates the MKSI shares came from restricted stock vesting events dated 02/15/2021 and 02/15/2022, totaling 9,633 and 367 shares respectively, and classifies these awards as compensation from the issuer.

Through which broker and market will the MKSI Form 144 sale occur?

The planned sale of 10,000 MKSI common shares is listed through Fidelity Brokerage Services LLC, to be executed on the NASDAQ market, with the approximate aggregate market value reported as $3,020,100.00.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 09:45 AM Accepted by SEC EDGAR 08/14/2026 - 09:44 AM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001414656
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	MKS INC
SEC File Number	000-23621
Address of Issuer	2 TECH DRIVE ANDOVER MASSACHUSETTS 01810
Phone	978-645-5500
Name of Person for Whose Account the Securities are To Be Sold	Lee John Tseng-Chung
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer
Relationship to Issuer	Director

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	10000	3020100.00	67617558	08/14/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	02/15/2021	Restricted Stock Vesting	Issuer			9633	02/15/2021	Compensation
Common	02/15/2022	Restricted Stock Vesting	Issuer			367	02/15/2022	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
John Tseng-Chung Lee 2 Tech Drive Andover MA 01810	Common	05/22/2026	10000	3154800.00

144: Remarks and Signature

Remarks
Date of Notice	08/14/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	02/20/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Tseng-Chung Lee
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)