Mark Massey

Net selling

Altarock Partners Lp — managed by Mark Massey; US equity positions disclosed quarterly via SEC 13F

Data as of 2026-03-31 (filed 2026-05-15) · Source: SEC EDGAR

Portfolio value$4.13B (−19%)

Holdings8

Top holdingAmazon.Com Inc

Below band0

New

Added

Exited

SEC 13F · latest filing

Holdings

Security	Value	Valuation	Holders	Shares	Weight	Signal
Amazon.Com IncAMZN	$1.58B	—	39	7,567,946	38.2%	Big new
Transdigm Group IncTDG	$1.05B	—	7	909,168	25.5%	Core 8q
Microsoft CorpMSFT	$691.3M	—	45	1,867,537	16.8%	Core 8q
Moodys CorpMCO	$376.1M	—	18	862,036	9.1%	Big new
Mastercard Inc-Class AMA	$261.2M	—	23	522,836	6.3%	Core 8q
Visa Inc-Class A ShrsV	$150.7M	—	30	498,677	3.7%	—
Alphabet Inc-Cl AGOOGL	$12.5M	—	43	43,391	0.3%	—
Hilton WorldwideHLT	$4.7M	—	6	15,341	0.1%	—

Amazon.Com IncAMZNBig new
Value$1.58BValuation—Holders39Weight38.2%
Transdigm Group IncTDGCore 8q
Value$1.05BValuation—Holders7Weight25.5%
Microsoft CorpMSFTCore 8q
Value$691.3MValuation—Holders45Weight16.8%
Moodys CorpMCOBig new
Value$376.1MValuation—Holders18Weight9.1%
Mastercard Inc-Class AMACore 8q
Value$261.2MValuation—Holders23Weight6.3%
Visa Inc-Class A ShrsV—
Value$150.7MValuation—Holders30Weight3.7%
Alphabet Inc-Cl AGOOGL—
Value$12.5MValuation—Holders43Weight0.3%
Hilton WorldwideHLT—
Value$4.7MValuation—Holders6Weight0.1%

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About this investor

Portfolio overview

Altarock Partners Lp's most recent 13F filing, for the quarter ended 2026-03-31, reports 8 positions worth $4.13B. The top 5 holdings represent 96% of that value, a concentrated portfolio.

The single largest position is Amazon.Com Inc at 38.2% of the portfolio, followed by Transdigm Group Inc at 25.5% and Microsoft Corp at 16.8%.

Against the prior quarter, Mark Massey opened 0 new positions, exited 0, added to 2, and trimmed 6.

Across all 8 quarters on file, Amazon.Com Inc has appeared in every filing, as has Transdigm Group Inc. Amazon.Com Inc currently ranks first by value.

A 13F is filed roughly 45 days after quarter-end and covers only long positions in US-listed equities, so it is a lagging and partial view of the portfolio. Source: SEC EDGAR.

Mark Massey has no positions in the strike zone right now. Browse the whole market by value band

Sources· SEC EDGAR 13F as of 2026-03-31 · filed 2026-05-15

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