MKSI (NASDAQ: MKSI) affiliate proposes sale of 6,000 shares; recent 2,500-share sale

Rhea-AI Filing Summary

MKSI affiliate disclosed a proposed sale of 6,000 shares of common stock, with an aggregate amount listed as $1,886,582.90 and a reference share count of 67,544,129 dated 06/01/2026. The filing notes prior sales of 2,500 shares by David Henry on 05/26/2026 for $826,250.00. Several prior issuances (ESPP purchases and restricted stock vesting) are itemized with dates and share counts.

Insights

Securities Compliance Analyst

Form 144 lists a proposed affiliate sale and recent dispositions.

The filing records a proposed sale of 6,000 shares with an aggregate amount of $1,886,582.90 and shows a recent disposition of 2,500 shares on 05/26/2026. This form is a notice required when affiliates propose to sell restricted or control securities.

Timing and execution mechanics are not specified in the excerpt; subsequent broker or Form 4 filings would show completion details.

Corporate Governance Advisor

Affiliate activity is routine but worth tracking for insider liquidity.

The excerpt lists issuer compensation vesting and ESPP purchases across multiple dates, indicating routine equity compensation activity. The David Henry sale of 2,500 shares on 05/26/2026 is shown as completed within the past three months.

Monitor future SEC reports for confirmations of execution or additional dispositions; the excerpt does not state purchaser identities or exact trade methods.

Key Figures

Proposed shares to be sold: 6,000 shares Aggregate amount listed: $1,886,582.90 Reference share count: 67,544,129 +4 more

7 metrics

Proposed shares to be sold 6,000 shares listed alongside Fidelity Brokerage Services LLC, dated 06/01/2026

Aggregate amount listed $1,886,582.90 associated with the 6,000-share line dated 06/01/2026

Reference share count 67,544,129 appears in same row as 06/01/2026 and NASDAQ

Recent sale - David Henry 2,500 shares sold on 05/26/2026 for $826,250.00

Recent sale proceeds $826,250.00 David Henry sale on 05/26/2026

ESPP purchase example 101 shares ESPP Purchase on 05/31/2022

Restricted stock vesting example 1,959 shares Restricted Stock Vesting on 02/15/2024

Key Terms

Form 144, ESPP Purchase, Restricted Stock Vesting, NASDAQ

4 terms

Form 144 regulatory

"144: Securities To Be Sold"

Form 144 is a document that investors must file with the government when they plan to sell a large number of shares of a company's stock. It helps ensure transparency so everyone knows how many shares are being sold and when, which can impact the stock's price.

ESPP Purchase financial

"05/31/2022 | ESPP Purchase | Issuer"

Restricted Stock Vesting financial

"04/15/2022 | Restricted Stock Vesting"

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.

NASDAQ market

"06/01/2026 | NASDAQ"

The Nasdaq is a stock exchange where many companies' shares are bought and sold, functioning much like a marketplace for investments. It matters to investors because it provides a platform to buy and sell ownership stakes in companies, helping them track the value of those companies and make informed decisions. As one of the largest and most technology-focused markets, it also reflects trends and developments in the business world.

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

144: Issuer Information

Name of Issuer

SEC File Number

Address of Issuer

Phone

Name of Person for Whose Account the Securities are To Be Sold

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

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	6000	1886582.90	67544129	06/01/2026	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	04/15/2022	Restricted Stock Vesting	Issuer			317	04/15/2022	Compensation
Common	05/31/2022	ESPP Purchase	Issuer			101	05/31/2022	Cash
Common	02/15/2024	Restricted Stock Vesting	Issuer			1959	02/15/2024	Compensation
Common	02/15/2025	Restricted Stock Vesting	Issuer			2852	02/15/2025	Compensation
Common	11/28/2025	ESPP Purchase	Issuer			86	11/28/2025	Cash
Common	02/15/2026	Restricted Stock Vesting	Issuer			685	02/15/2026	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
David Henry 2 Tech Drive Andover MA 01810	Common	05/26/2026	2500	826250.00

144: Remarks and Signature

Remarks

Date of Notice

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

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

FAQ

What does MKSI's Form 144 disclose about proposed sales?

It lists a proposed sale of 6,000 shares totaling $1,886,582.90. The form is a notice by an affiliate; it does not by itself confirm the trades were completed and provides limited execution details.

Who recently sold MKSI shares according to the filing?

David Henry sold 2,500 shares on 05/26/2026 for $826,250.00. That transaction is reported in the "Securities Sold During The Past 3 Months" section of the excerpt.

Are the shares from compensation or purchases listed in the filing?

The excerpt itemizes ESPP purchases and restricted stock vesting entries. Examples include ESPP purchases on 05/31/2022 (101 shares) and vesting on 02/15/2024 (1,959 shares).

Does the Form 144 confirm how the proposed sale will be executed?

No — execution method and timing are not specified in the excerpt. Form 144 provides notice of intent; later filings or broker reports would show execution details if trades occur.