William D Stewart

CIK 1202731 · View on SEC EDGAR ↗

Insider

First SEC filing: Feb. 4, 2004 · Latest: Jan. 20, 2012

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Insider at Companies where this person is a reporting insider.
Insider transactions Every share this person bought or sold, from Form 4 filings.
Derivatives Options and other derivative holdings reported by this person.

Insider at

MKSI selling Feb. 13, 2012

Insider transactions

0 buys (P) 0 sells (S) Net: $0 + 87 non-open-market transactions below last 12 months, based on the transactions shown below

Price change vs current quote, split-adjusted for corporate actions since the filing — not benchmarked, not annualized, not size-weighted

87 other filings hidden

Date	Ticker	Code	Shares	Price	Value	Owned after	Δ own	A/D	vs now
April 2, 2012	MKSI	A	1,684	—	—	3,268 Indirect	+106.31%	Acquired	(price as of 2026-08-20)
April 2, 2012	MKSI	M	6,037	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
April 2, 2012	MKSI	M	5,592	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
April 2, 2012	MKSI	F 10b5-1	3,617	$29.70	$107,425	15,261 Direct	-19.16%	Disposed	829.3% (price as of 2026-08-20)
April 2, 2012	MKSI	M	6,037	—	—	18,878 Direct	+47.01%	Acquired	(price as of 2026-08-20)
April 2, 2012	MKSI	M	5,592	—	—	12,841 Direct	+77.14%	Acquired	(price as of 2026-08-20)
March 16, 2012	MKSI	M	1,400	—	—	6,037 Direct	-18.82%	Disposed	(price as of 2026-08-20)
March 16, 2012	MKSI	M	1,960	—	—	5,592 Direct	-25.95%	Disposed	(price as of 2026-08-20)
March 16, 2012	MKSI	F 10b5-1	1,046	$29.60	$30,962	7,249 Direct	-12.61%	Disposed	832.4% (price as of 2026-08-20)
March 16, 2012	MKSI	M	1,400	—	—	8,295 Direct	+20.30%	Acquired	(price as of 2026-08-20)
March 16, 2012	MKSI	M	1,960	—	—	6,895 Direct	+39.72%	Acquired	(price as of 2026-08-20)
March 5, 2012	MKSI	M	2,000	—	—	7,437 Direct	-21.19%	Disposed	(price as of 2026-08-20)
March 5, 2012	MKSI	M	2,700	—	—	7,552 Direct	-26.34%	Disposed	(price as of 2026-08-20)
March 5, 2012	MKSI	F 10b5-1	1,462	$28.46	$41,609	4,935 Direct	-22.85%	Disposed	869.7% (price as of 2026-08-20)
March 5, 2012	MKSI	M	2,000	—	—	6,397 Direct	+45.49%	Acquired	(price as of 2026-08-20)
March 5, 2012	MKSI	M	2,700	—	—	4,397 Direct	+159.10%	Acquired	(price as of 2026-08-20)
Feb. 28, 2012	MKSI	M	1,018	—	—	9,437 Direct	-9.74%	Disposed	(price as of 2026-08-20)
Feb. 28, 2012	MKSI	M	1,446	—	—	10,252 Direct	-12.36%	Disposed	(price as of 2026-08-20)
Feb. 28, 2012	MKSI	F 10b5-1	767	$30.63	$23,493	1,697 Direct	-31.13%	Disposed	801.0% (price as of 2026-08-20)
Feb. 28, 2012	MKSI	M	1,018	—	—	2,464 Direct	+70.40%	Acquired	(price as of 2026-08-20)
Feb. 28, 2012	MKSI	M	1,446	—	—	1,446 Direct	—	Acquired	(price as of 2026-08-20)
Feb. 27, 2012	MKSI	J	122	—	—	12,020 Direct	-1.00%	Disposed	(price as of 2026-08-20)
Feb. 27, 2012	MKSI	J	122	—	—	11,898 Direct	-1.01%	Disposed	(price as of 2026-08-20)
Feb. 13, 2012	MKSI	S	188	$31.98	$6,012	1 Indirect	-99.47%	Disposed	763.0% (price as of 2026-08-20)
Aug. 9, 2011	MKSI	S	8,575	$22.46	$192,594	0 Direct	-100.00%	Disposed	1128.8% (price as of 2026-08-20)
May 3, 2011	MKSI	M	1,000	—	—	10,455 Direct	-8.73%	Disposed	(price as of 2026-08-20)
May 3, 2011	MKSI	F	311	$25.85	$8,039	8,575 Direct	-3.50%	Disposed	967.7% (price as of 2026-08-20)
May 3, 2011	MKSI	M	1,000	—	—	8,886 Direct	+12.68%	Acquired	(price as of 2026-08-20)
March 16, 2011	MKSI	M	1,400	—	—	11,455 Direct	-10.89%	Disposed	(price as of 2026-08-20)
March 16, 2011	MKSI	M	1,960	—	—	12,143 Direct	-13.90%	Disposed	(price as of 2026-08-20)
March 16, 2011	MKSI	F 10b5-1	1,046	$28.51	$29,821	7,886 Direct	-11.71%	Disposed	868.0% (price as of 2026-08-20)
March 16, 2011	MKSI	M	1,400	—	—	8,932 Direct	+18.59%	Acquired	(price as of 2026-08-20)
March 16, 2011	MKSI	M	1,960	—	—	7,532 Direct	+35.18%	Acquired	(price as of 2026-08-20)
March 10, 2011	MKSI	M	2,000	—	—	12,855 Direct	-13.46%	Disposed	(price as of 2026-08-20)
March 10, 2011	MKSI	M	1,388	—	—	14,103 Direct	-8.96%	Disposed	(price as of 2026-08-20)
March 10, 2011	MKSI	F 10b5-1	1,054	$29.53	$31,125	5,572 Direct	-15.91%	Disposed	834.6% (price as of 2026-08-20)
March 10, 2011	MKSI	M	2,000	—	—	6,626 Direct	+43.23%	Acquired	(price as of 2026-08-20)
March 10, 2011	MKSI	M	1,388	—	—	4,626 Direct	+42.87%	Acquired	(price as of 2026-08-20)
March 4, 2011	MKSI	M	2,000	—	—	14,855 Direct	-11.87%	Disposed	(price as of 2026-08-20)
March 4, 2011	MKSI	M	2,700	—	—	15,491 Direct	-14.84%	Disposed	(price as of 2026-08-20)
March 4, 2011	MKSI	F 10b5-1	1,462	$32.05	$46,857	3,238 Direct	-31.11%	Disposed	761.1% (price as of 2026-08-20)
March 4, 2011	MKSI	M	2,000	—	—	4,700 Direct	+74.07%	Acquired	(price as of 2026-08-20)
March 4, 2011	MKSI	M	2,700	—	—	2,700 Direct	—	Acquired	(price as of 2026-08-20)
Feb. 28, 2011	MKSI	A	4,583	—	—	18,191 Direct	+33.68%	Acquired	(price as of 2026-08-20)
Feb. 28, 2011	MKSI	A	3,055	—	—	16,855 Direct	+22.14%	Acquired	(price as of 2026-08-20)
Feb. 17, 2011	MKSI	J	200	—	—	13,408 Direct	-1.47%	Disposed	(price as of 2026-08-20)
Feb. 17, 2011	MKSI	J	100	—	—	13,608 Direct	-0.73%	Disposed	(price as of 2026-08-20)
Feb. 10, 2011	MKSI	M	24,000	$27.11	$650,640	24,000 Direct	—	Acquired	918.0% (price as of 2026-08-20)
Feb. 10, 2011	MKSI	S	24,000	$30.00	$720,000	0 Direct	-100.00%	Disposed	820.0% (price as of 2026-08-20)
Feb. 10, 2011	MKSI	M	24,000	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
May 3, 2010	MKSI	A	3,000	—	—	13,800 Direct	+27.78%	Acquired	(price as of 2026-08-20)
March 25, 2010	MKSI	M 10b5-1	1,875	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
March 25, 2010	MKSI	S 10b5-1	8,914	$19.50	$173,823	0 Direct	-100.00%	Disposed	1315.3% (price as of 2026-08-20)
March 25, 2010	MKSI	M 10b5-1	1,875	$14.72	$27,600	8,914 Direct	+26.64%	Acquired	1774.9% (price as of 2026-08-20)
March 16, 2010	MKSI	M	1,400	—	—	10,800 Direct	-11.48%	Disposed	(price as of 2026-08-20)
March 16, 2010	MKSI	M	1,960	—	—	13,708 Direct	-12.51%	Disposed	(price as of 2026-08-20)
March 16, 2010	MKSI	F 10b5-1	1,046	$19.29	$20,177	7,039 Direct	-12.94%	Disposed	1330.7% (price as of 2026-08-20)
March 16, 2010	MKSI	M	1,400	—	—	8,085 Direct	+20.94%	Acquired	(price as of 2026-08-20)
March 16, 2010	MKSI	M	1,960	—	—	6,685 Direct	+41.48%	Acquired	(price as of 2026-08-20)
March 10, 2010	MKSI	M	1,388	—	—	3,779 Direct	+58.05%	Acquired	(price as of 2026-08-20)
March 10, 2010	MKSI	M	2,000	—	—	5,779 Direct	+52.92%	Acquired	(price as of 2026-08-20)
March 10, 2010	MKSI	F 10b5-1	1,054	$19.07	$20,100	4,725 Direct	-18.24%	Disposed	1347.2% (price as of 2026-08-20)
March 10, 2010	MKSI	M	1,388	—	—	15,668 Direct	-8.14%	Disposed	(price as of 2026-08-20)
March 10, 2010	MKSI	M	2,000	—	—	12,200 Direct	-14.08%	Disposed	(price as of 2026-08-20)
March 4, 2010	MKSI	A	6,000	—	—	14,200 Direct	+73.17%	Acquired	(price as of 2026-08-20)
March 4, 2010	MKSI	A	8,400	—	—	16,976 Direct	+97.95%	Acquired	(price as of 2026-08-20)
March 1, 2010	MKSI	M	3,787	—	—	16,856 Direct	-18.35%	Disposed	(price as of 2026-08-20)
March 1, 2010	MKSI	F 10b5-1	1,396	$18.35	$25,617	2,391 Direct	-36.86%	Disposed	1404.0% (price as of 2026-08-20)
March 1, 2010	MKSI	M	3,787	—	—	3,787 Direct	—	Acquired	(price as of 2026-08-20)
Aug. 3, 2009	MKSI	S	12,906	$19.60	$252,958	0 Direct	-100.00%	Disposed	1308.1% (price as of 2026-08-20)
March 16, 2009	MKSI	A	8,400	—	—	18,963 Direct	+79.52%	Acquired	(price as of 2026-08-20)
March 10, 2009	MKSI	M	3,388	—	—	10,563 Direct	-24.28%	Disposed	(price as of 2026-08-20)
March 10, 2009	MKSI	F 10b5-1	1,054	$12.19	$12,848	12,906 Direct	-7.55%	Disposed	2164.1% (price as of 2026-08-20)
March 10, 2009	MKSI	M	3,388	—	—	13,960 Direct	+32.05%	Acquired	(price as of 2026-08-20)
March 2, 2009	MKSI	M	3,786	—	—	15,787 Direct	-19.34%	Disposed	(price as of 2026-08-20)
March 2, 2009	MKSI	S	1,178	$11.89	$14,006	10,572 Direct	-10.03%	Disposed	2221.2% (price as of 2026-08-20)
March 2, 2009	MKSI	M	3,786	—	—	11,750 Direct	+47.54%	Acquired	(price as of 2026-08-20)
Feb. 13, 2009	MKSI	F 10b5-1	4,036	$15.89	$64,132	7,964 Direct	-33.63%	Disposed	1636.9% (price as of 2026-08-20)
May 19, 2008	MKSI	S	3,102	$25.72	$79,783	12,000 Direct	-20.54%	Disposed	973.1% (price as of 2026-08-20)
May 19, 2008	MKSI	M	7,500	—	—	1,875 Direct	-80.00%	Disposed	(price as of 2026-08-20)
May 19, 2008	MKSI	S	7,500	$25.64	$192,300	15,102 Direct	-33.18%	Disposed	976.4% (price as of 2026-08-20)
May 19, 2008	MKSI	M	7,500	$14.72	$110,400	22,602 Direct	+49.66%	Acquired	1774.9% (price as of 2026-08-20)
March 10, 2008	MKSI	A	12,000	—	—	20,214 Direct	+146.09%	Acquired	(price as of 2026-08-20)
March 1, 2008	MKSI	M	3,786	—	—	8,214 Direct	-31.55%	Disposed	(price as of 2026-08-20)
March 1, 2008	MKSI	F	1,347	—	—	15,102 Direct	-8.19%	Disposed	(price as of 2026-08-20)
March 1, 2008	MKSI	M	3,786	—	—	16,449 Direct	+29.90%	Acquired	(price as of 2026-08-20)
June 11, 2007	MKSI	M	133	—	—	11,000 Direct	-1.19%	Disposed	(price as of 2026-08-20)
June 11, 2007	MKSI	S	133	$27.40	$3,644	12,663 Direct	-1.04%	Disposed	907.3% (price as of 2026-08-20)
June 11, 2007	MKSI	M	133	$24.50	$3,258	12,796 Direct	+1.05%	Acquired	1026.5% (price as of 2026-08-20)
June 4, 2007	MKSI	M	7,448	—	—	11,133 Direct	-40.08%	Disposed	(price as of 2026-08-20)
June 4, 2007	MKSI	S	7,448	$27.40	$204,075	12,663 Direct	-37.03%	Disposed	907.3% (price as of 2026-08-20)
June 4, 2007	MKSI	M	7,448	$24.50	$182,476	20,111 Direct	+58.82%	Acquired	1026.5% (price as of 2026-08-20)
June 1, 2007	MKSI	M	15,990	—	—	3,565 Direct	-81.77%	Disposed	(price as of 2026-08-20)
June 1, 2007	MKSI	S	15,990	$27.42	$438,446	12,663 Direct	-55.81%	Disposed	906.5% (price as of 2026-08-20)
June 1, 2007	MKSI	M	15,990	$24.50	$391,755	28,653 Direct	+126.27%	Acquired	1026.5% (price as of 2026-08-20)
May 31, 2007	MKSI	M	20,000	—	—	19,555 Direct	-50.56%	Disposed	(price as of 2026-08-20)
May 31, 2007	MKSI	S	10,000	$27.23	$272,300	12,663 Direct	-44.12%	Disposed	913.6% (price as of 2026-08-20)
May 31, 2007	MKSI	S	10,000	$27.19	$271,900	22,663 Direct	-30.62%	Disposed	915.0% (price as of 2026-08-20)
May 31, 2007	MKSI	M	20,000	$24.50	$490,000	32,663 Direct	+157.94%	Acquired	1026.5% (price as of 2026-08-20)
May 22, 2007	MKSI	M	13,700	—	—	3,565 Direct	-79.35%	Disposed	(price as of 2026-08-20)

Showing latest 100 of 175 transactions

P = Open-market purchase · S = Sale · A = Grant/award · M = Option exercise · G = Gift · F = Tax withholding

Insider transactions are not a recommendation; sales are often driven by liquidity or tax reasons.

Derivative holdings (Form 4 Table II)

Options, RSUs and convertible securities reported on Form 4 Table II.

Date	Ticker	Security	Underlying	Exercise price	Expiration	Shares	A/D
April 2, 2012	MKSI	Restricted Stock Unit	Common Stock (1,684)	—	—	1,684	Acquired
April 2, 2012	MKSI	Restricted Stock Unit	Common Stock (6,037)	—	—	6,037	Disposed
April 2, 2012	MKSI	Restricted Stock Unit	Common Stock (5,592)	—	—	5,592	Disposed
March 16, 2012	MKSI	Restricted Stock Unit	Common Stock (1,400)	—	—	1,400	Disposed
March 16, 2012	MKSI	Restricted Stock Unit	Common Stock (1,960)	—	—	1,960	Disposed
March 5, 2012	MKSI	Restricted Stock Unit	Common Stock (2,000)	—	—	2,000	Disposed
March 5, 2012	MKSI	Restricted Stock Unit	Common Stock (2,700)	—	—	2,700	Disposed
Feb. 28, 2012	MKSI	Restricted Stock Unit	Common Stock (1,018)	—	—	1,018	Disposed
Feb. 28, 2012	MKSI	Restricted Stock Unit	Common Stock (1,446)	—	—	1,446	Disposed
Feb. 27, 2012	MKSI	Restricted Stock Unit	Common Stock (122)	—	—	122	Disposed
Feb. 27, 2012	MKSI	Restricted Stock Unit [F1]	Common Stock (122)	—	—	122	Disposed
May 3, 2011	MKSI	Restricted Stock Unit	Common Stock (1,000)	—	—	1,000	Disposed
March 16, 2011	MKSI	Restricted Stock Unit	Common Stock (1,400)	—	—	1,400	Disposed
March 16, 2011	MKSI	Restricted Stock Unit	Common Stock (1,960)	—	—	1,960	Disposed
March 10, 2011	MKSI	Restricted Stock Unit	Common Stock (2,000)	—	—	2,000	Disposed
March 10, 2011	MKSI	Restricted Stock Unit	Common Stock (1,388)	—	—	1,388	Disposed
March 4, 2011	MKSI	Restricted Stock Unit	Common Stock (2,000)	—	—	2,000	Disposed
March 4, 2011	MKSI	Restricted Stock Unit	Common Stock (2,700)	—	—	2,700	Disposed
Feb. 28, 2011	MKSI	Restricted Stock Unit	Common Stock (4,583)	—	—	4,583	Acquired
Feb. 28, 2011	MKSI	Restricted Stock Unit	Common Stock (3,055)	—	—	3,055	Acquired
Feb. 17, 2011	MKSI	Restricted Stock Unit [F1]	Common Stock (200)	—	—	200	Disposed
Feb. 17, 2011	MKSI	Restricted Stock Unit	Common Stock (0)	—	—	100	Disposed
Feb. 10, 2011	MKSI	Stock Option (Right to Buy)	Common Stock (24,000)	$27.11	Nov. 13, 2013	24,000	Disposed
May 3, 2010	MKSI	Restricted Stock Unit	Common Stock (3,000)	—	—	3,000	Acquired
March 25, 2010	MKSI	Stock Option (Right to Buy)	Common Stock (1,875)	$14.72	July 30, 2014	1,875	Disposed
March 16, 2010	MKSI	Restricted Stock Unit	Common Stock (1,400)	—	—	1,400	Disposed
March 16, 2010	MKSI	Restricted Stock Unit	Common Stock (1,960)	—	—	1,960	Disposed
March 10, 2010	MKSI	Restricted Stock Unit	Common Stock (1,388)	—	—	1,388	Disposed
March 10, 2010	MKSI	Restricted Stock Unit	Common Stock (2,000)	—	—	2,000	Disposed
March 4, 2010	MKSI	Restricted Stock Unit	Common Stock (6,000)	—	—	6,000	Acquired
March 4, 2010	MKSI	Restricted Stock Unit	Common Stock (8,400)	—	—	8,400	Acquired
March 1, 2010	MKSI	Restricted Stock Unit	Common Stock (3,787)	—	—	3,787	Disposed
March 16, 2009	MKSI	Restricted Stock Unit	Common Stock (8,400)	—	—	8,400	Acquired
March 10, 2009	MKSI	Restricted Stock Unit	Common Stock (3,388)	—	—	3,388	Disposed
March 2, 2009	MKSI	Restricted Stock Unit	Common Stock (3,786)	—	—	3,786	Disposed
May 19, 2008	MKSI	Stock Option (Right to Buy)	Common (7,500)	$14.72	July 30, 2014	7,500	Disposed
March 10, 2008	MKSI	Restricted Stock Unit	Common (12,000)	—	—	12,000	Acquired
March 1, 2008	MKSI	Restricted Stock Unit	Common (3,786)	—	—	3,786	Disposed
June 11, 2007	MKSI	Stock Option (right to buy)	Common (133)	—	Aug. 8, 1988	133	Disposed
June 4, 2007	MKSI	Stock Option (right to buy)	Common (7,448)	—	Aug. 8, 1988	7,448	Disposed
June 1, 2007	MKSI	Stock Option (right to buy)	Common (15,990)	—	Aug. 8, 1988	15,990	Disposed
May 31, 2007	MKSI	Stock Option (right to buy)	Common (20,000)	—	Aug. 8, 1988	20,000	Disposed
May 22, 2007	MKSI	Stock Option (right to buy)	Common (13,700)	—	Aug. 8, 1988	13,700	Disposed
May 22, 2007	MKSI	Stock Option (right to buy)	Common (4,125)	—	Aug. 8, 1988	4,125	Disposed
May 21, 2007	MKSI	Stock Option (right to buy)	Common (6,300)	—	Aug. 8, 1988	6,300	Disposed
May 21, 2007	MKSI	Stock Option (right to buy)	Common (5,500)	—	Aug. 8, 1988	5,500	Disposed
May 21, 2007	MKSI	Stock Option (right to buy)	Common (1,875)	—	Aug. 8, 1988	1,875	Disposed
May 21, 2007	MKSI	Stock Option (right to buy)	Common (9,375)	—	Aug. 8, 1988	9,375	Disposed
May 7, 2007	MKSI	Stock Option (right to buy)	Common (1,972)	—	Aug. 8, 1988	1,972	Disposed
May 4, 2007	MKSI	Stock Option (right to buy)	Common (24,557)	—	Aug. 8, 1988	24,557	Disposed
May 2, 2007	MKSI	Stock Option (right to buy)	Common (34,900)	—	Aug. 8, 1988	34,900	Disposed
May 2, 2007	MKSI	Stock Option (right to buy)	Common (15,375)	—	Aug. 8, 1988	15,375	Disposed
May 2, 2007	MKSI	Stock Option (right to buy)	Common (1,875)	—	Aug. 8, 1988	1,875	Disposed
May 2, 2007	MKSI	Stock Option (right to buy)	Common (3,750)	—	Aug. 8, 1988	3,750	Disposed
April 16, 2007	MKSI	Stock Option (right to buy)	Common (28,125)	—	Aug. 8, 1988	28,125	Disposed
March 1, 2007	MKSI	Restricted Stock Unit	Common (12,000)	—	—	12,000	Acquired
Feb. 15, 2007	MKSI	Stock Option (right to buy)	Common (37,500)	—	Aug. 8, 1988	37,500	Disposed
Feb. 15, 2007	MKSI	Stock Option (right to buy)	Common (15,000)	—	Aug. 8, 1988	15,000	Disposed
Feb. 15, 2007	MKSI	Stock Option (right to buy)	Common (3,750)	—	Aug. 8, 1988	3,750	Disposed
April 19, 2006	MKSI	Stock Option (right to buy)	Common (381)	—	Aug. 8, 1988	381	Disposed
April 19, 2006	MKSI	Stock Option (right to buy)	Common (24,375)	—	Aug. 8, 1988	24,375	Disposed
April 19, 2006	MKSI	Stock Option (right to buy)	Common (490)	—	Aug. 8, 1988	490	Disposed
April 19, 2006	MKSI	Stock Option (right to buy)	Common (926)	—	Aug. 8, 1988	926	Disposed
April 19, 2006	MKSI	Stock Option (right to buy)	Common (30,000)	—	Aug. 8, 1988	30,000	Disposed
Feb. 14, 2005	MKSI	Stock Option (right to buy)	Common (75,000)	—	Aug. 8, 1988	75,000	Acquired
Feb. 14, 2005	MKSI	Stock Option (right to buy)	Common (37,500)	—	Aug. 8, 1988	37,500	Acquired
Dec. 6, 2004	MKSI	Stock Option (right to Buy)	Common (490)	$12.97	Aug. 8, 1988	490	Disposed
Dec. 6, 2004	MKSI	Stock Option (right to buy)	Common (81,600)	$0.00	Aug. 8, 1988	81,600	Disposed
July 30, 2004	MKSI	Stock Option (Right to Buy)	Common (30,000)	$14.72	July 30, 2014	30,000	Acquired
Jan. 5, 2004	MKSI	Stock Option (roght to buy)	Common (6,000)	$29.93	Jan. 6, 2014	6,000	Acquired
Jan. 5, 2004	MKSI	Stock Option (right to buy)	Common (30,000)	$0.00	Aug. 8, 1988	30,000	Disposed
Nov. 11, 2003	MKSI	Stock Option (right to buy)	Common (24,000)	$27.11	Nov. 13, 2013	24,000	Acquired

Exercise/conversion price is blank when not applicable (e.g. RSUs).