MKSI · Insider Trading

MKS Inc. Common Stock

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Every open-market purchase and sale reported by MKSI officers, directors and 10%+ beneficial owners on SEC Form 4, which must be filed within two business days of the transaction. Sales often reflect scheduled 10b5-1 plans or tax withholding rather than a directional view, so read counts alongside the size and the filer.

Form 4 Filings

most recent

Open-Market Buys

code P

Sales

code S

Reporting Insiders

current holders

MKSI — Recent Form 4 Transactions (latest 2026-09-02)

Filed	Insider	Role	Type	Shares	Value
2026-09-02	Elizabeth Mora	Director	Sell	−300	−$75.29K
2026-08-18	Renee Martel Donlan	EVP, GC & CCO	A	+954 deriv.	—
2026-08-17	John Tseng-Chung Lee	President & CEO	Sell	−10,000	−$3.02M
2026-08-04	John Edward Williams	EVP & GM, PSD	Sell	−457	−$131.76K
2026-06-16	James Alan Schreiner	EVP & COO	Sell	−3,500	−$1.21M
2026-06-11	James Alan Schreiner	EVP & COO	Sell	−781	−$247.91K
2026-06-08	Michelle M McCarthy	SVP & Chief Accounting Officer	Sell	−2,434	−$767.27K
2026-06-02	Elizabeth Mora	Director	Sell	−300	−$95.41K
2026-06-02	David Philip Henry	EVP, Global Str Mktg & GM, MSD	Sell	−6,000	−$1.89M
2026-05-28	Gerald G Colella	Director	Sell	−20,000	−$6.67M
2026-05-28	Joseph B Donahue	Director	Sell	−2,100	−$688.70K
2026-05-27	David Philip Henry	EVP, Global Str Mktg & GM, MSD	Sell	−2,500	−$826.25K
2026-05-26	John Tseng-Chung Lee	President & CEO	Sell	−10,000	−$3.15M
2026-05-26	Ramakumar Mayampurath	EVP & CFO	Sell	−8,810	−$2.78M
2026-05-19	Peter Cannone III	Director	Sell	−1,350	−$409.59K
2026-05-15	Jacqueline F Moloney	Director	Sell	−1,000	−$312.20K
2026-05-14	Jacqueline F Moloney	Director	Sell	−1,400	−$446.59K
2026-05-12	Gerald G Colella	Director	A	+781	—
2026-05-12	Raj Batra	Director	A	+781	—
2026-05-12	Peter Cannone III	Director	A	+781	—
2026-05-12	Joseph B Donahue	Director	A	+781	—
2026-05-12	Kathleen Flaherty Burke	EVP, GC & Secretary	Sell	−4,355	−$1.39M
2026-05-12	Elizabeth Mora	Director	A	+781	—
2026-05-12	Wissam G Jabre	Director	A	+781	—
2026-05-12	Jacqueline F Moloney	Director	A	+781	—
2026-05-12	Eric Robert Taranto	EVP & GM, VSD	Sell	−2,848	−$911.33K
2026-04-20	John Edward Williams	EVP & GM, PSD	MIXED	+914	−$222.92K
2026-04-16	Michelle M McCarthy	SVP & Chief Accounting Officer	MIXED	+2,435	−$377.08K
2026-03-13	Jacqueline F Moloney	Director	Sell	−340	−$72.71K
2026-03-09	Eric Robert Taranto	EVP & GM, VSD	Sell	−4,567	−$1.01M
2026-03-03	Elizabeth Mora	Director	Sell	−300	−$71.83K
2026-02-25	James Alan Schreiner	EVP & COO	Sell	−4,100	−$1.05M
2026-02-24	Gerald G Colella	Director	Sell	−20,000	−$5.07M
2026-02-23	John Tseng-Chung Lee	President & CEO	Sell	−30,000	−$7.70M
2026-02-23	Kathleen Flaherty Burke	EVP, GC & Secretary	Sell	−4,254	−$1.06M
2026-02-23	John Edward Williams	EVP & GM, PSD	Sell	−2,042	−$523.74K
2026-02-23	Jacqueline F Moloney	Director	Sell	−829	−$205.22K
2026-02-23	Michelle M McCarthy	VP & Chief Accounting Officer	Sell	−1,466	−$366.50K
2026-02-23	David Philip Henry	EVP, Global Str Mktg & GM, MSD	Sell	−2,000	−$523.12K
2026-02-23	Eric Robert Taranto	EVP & GM, VSD	Sell	−1,452	−$359.62K
2026-02-23	Peter Cannone III	Director	Sell	−1,250	−$322.57K
2026-02-18	John Tseng-Chung Lee	President & CEO	MIXED	+37,340	−$8.49M
2026-02-18	Kathleen Flaherty Burke	EVP, GC & Secretary	MIXED	+6,888	−$1.39M
2026-02-18	Ramakumar Mayampurath	EVP & CFO	MIXED	+3,144	−$656.01K
2026-02-18	John Edward Williams	EVP & GM, PSD	MIXED	+2,042	−$311.71K
2026-02-18	James Alan Schreiner	EVP & COO	MIXED	+4,881	−$1.13M
2026-02-18	David Philip Henry	EVP, Global Str Mktg & GM, MSD	MIXED	+5,184	−$1.07M
2026-02-18	Eric Robert Taranto	EVP & GM, VSD	MIXED	+3,761	−$707.07K
2026-02-09	John Tseng-Chung Lee	President & CEO	A	+50,971 deriv.	—
2026-02-09	Ramakumar Mayampurath	EVP & CFO	A	+8,877 deriv.	—

MKSI — Current Insider Holders

Insider	Role	Shares Held	Value
John Tseng-Chung Lee	President & CEO	134,776	$26.43M
Kathleen Flaherty Burke	EVP, GC & Secretary	49,439	$9.70M
Gerald G Colella	Director	33,654	$6.60M
James Alan Schreiner	EVP & COO	20,230	$3.97M
Elizabeth Mora	Director	18,845	$3.70M
Raj Batra	Director	16,227	$3.18M
Eric Robert Taranto	EVP & GM, VSD	12,596	$2.47M
David Philip Henry	EVP, Global Str Mktg & GM, MSD	10,421	$2.04M
Joseph B Donahue	Director	10,032	$1.97M
Jacqueline F Moloney	Director	8,775	$1.72M
Peter Cannone III	Director	7,794	$1.53M
Wissam G Jabre	Director	5,269	$1.03M
John Edward Williams	EVP & GM, PSD	4,097	$803.63K
Michelle M McCarthy	SVP & Chief Accounting Officer	1	$304
Ramakumar Mayampurath	EVP & CFO	1	$223

MKSI Insider Trading FAQ

Who are the insiders at MKSI?

15 officers, directors and 10%+ beneficial owners currently report holdings in MKSI via SEC Form 4.

Are MKSI insiders buying or selling?

Across the 50 most recent Form 4 filings for MKSI, 0 were open-market purchases (code P) and 31 were sales (code S). Sales frequently reflect scheduled 10b5-1 plans or tax withholding rather than a view on the stock.

How current is MKSI insider data?

Form 4 must be filed within two business days of the transaction, so this is close to real time. The most recent MKSI filing is dated 2026-09-02.

How to read Form 4 activity

Form 4 reports a change in beneficial ownership by an officer, director or 10%+ holder, and must be filed within two business days of the transaction — so this is close to real time, unlike the 45-day-lagged 13F institutional data.

Transaction codes matter more than the raw buy/sell count. Code P is an open-market purchase — an insider choosing to buy with their own money, which is the signal most research treats as informative. Code S is a sale, but sales are frequently pre-scheduled under a 10b5-1 plan or cover tax withholding on vesting equity, so a run of sales often says nothing directional. Codes A and M are grants and option exercises rather than open-market decisions.

Full filing history and per-insider positions are on the MKSI quote page; the site-wide leaderboard is on the insider transactions hub.