WESTFIELD CAPITAL MANAGEMENT CO LP

Position in MKSI — Mks Inc

CIK 1177719 BOSTON, MA

Position in MKSI

as of Jun 30, 2026 · filed Aug 12, 2026 Compact

Position Value

$413,048,841

+$172,492,236 QoQ

Shares Held

928,617

-11.3% QoQ

Ownership

1.37%

of shares outstanding

% of Portfolio

1.36%

of 13F equity value

Holder Rank

#19

of 773 holders

Holding Since

Mar 2020

18 quarters on record

Voting authority Sole 85% Shared 0% None 15%

Technology · as of Jun 30, 2026

WESTFIELD CAPITAL MANAGEMENT CO LP holds $843,296,253 across 5 Scientific & Technical Instruments names. MKSI ranks #1 (49.0% of the industry book) .

#	Ticker	Company	Shares	Value (USD)
1	MKSI	Mks Inc This page	928,617	$413,048,841
2	GRMN	Garmin Ltd	861,057	$204,535,479
3	COHR	Coherent Corp.	291,040	$114,806,548
4	ST	Sensata Technologies Holding plc	1,333,853	$63,678,142
5	KEYS	Keysight Technologies, Inc.	134,908	$47,227,243

18 filing rows on record

Report Date	Value (USD)	Shares	Change	Type	Discretion	Filed
2026-06-30	$413,048,841	928,617	-11.3%	Shares	Sole	2026-08-12
2026-03-31	$240,556,605	1,046,763	+24.6%	Shares	Sole	2026-05-11
2025-12-31	$134,195,725	839,773	+159.7%	Shares	Sole	2026-02-11
2025-09-30	$40,022,762	323,364	+1241.8%	Shares	Sole	2025-11-12
2024-09-30	$2,619,911	24,100	0.0%	Shares	Sole	2024-11-12
2024-06-30	$3,146,978	24,100	-96.1%	Shares	Sole	2024-08-14
2024-03-31	$82,468,379	620,063	+5.1%	Shares	Sole	2024-05-10
2023-12-31	$60,663,982	589,715	-23.3%	Shares	Sole	2024-02-09
2022-09-30	$63,504,460	768,447	+8.7%	Shares	Sole	2022-11-14
2022-06-30	$72,575,830	707,160	+22.6%	Shares	Sole	2022-08-12
2022-03-31	$86,496,450	576,643	+4.1%	Shares	Sole	2022-05-16
2021-09-30	$83,599,914	553,972	+54.7%	Shares	Sole	2021-11-12
2021-06-30	$63,706,633	358,003	+10.3%	Shares	Sole	2021-08-10
2021-03-31	$60,160,816	324,457	-1.3%	Shares	Sole	2021-05-14
2020-12-31	$49,456,676	328,725	+13.0%	Shares	Sole	2021-02-12
2020-09-30	$31,785,493	290,996	+42.2%	Shares	Sole	2020-11-13
2020-06-30	$23,172,867	204,635	-19.7%	Shares	Sole	2020-08-13
2020-03-31	$20,768,935	254,990	—	Shares	Sole	2020-05-14
No filing history on record for this holder in this stock.