MASON CAPITAL MANAGEMENT LLC

CIK

1218735

Location

New York, NY

Portfolio Value

Small $524,410,108

Diversification

Highly concentrated

Filing Date

Global Rank

#2,551 / 8,623 ▼ 54 · as of Mar 2026

Top Industry

Specialty Industrial Machinery 88.2%

3Y Alpha vs SPY

-31.5%

Period ended 4 months ago

Filed May 15, 2026 · 3mo

25 quarters · since Mar 2020

Clone Performance

Jul 2023–Jul 2026 · vs SPY

Hypothetical growth of buying every stock this filer reported holding, rebalancing on each filing and indexed to the same start. Option positions cannot be bought this way and are left out.

Cloned portfolio

-34.6%

SPY

+65.3%

Annualised alpha

-31.4%

Max drawdown

−52.2%

Estimate. 13F holdings are quarter-lagged, so the clone rebalances about 45 days after each period end — when the filing becomes public — and it excludes option and short positions. It tracks 100% of reported value on average across 13 quarters. Past performance does not predict future results.

Portfolio Concentration

6 tracked positions · as of Mar 31, 2026 · Δ vs Dec 31, 2025

Top Position

88.2%

+11.8 pts

Top 5

100.0%

+4.0 pts

Top 10

100.0%

0.0 pts

HHI

7,837

Highly concentrated+1,894

Portfolio Trend

25 quarters · across all stocks

Sector Breakdown

As of Mar 31, 2026

Sector	% Portfolio	Value	Positions
Industrials	88.4%	$463,560,931	3
Healthcare	5.8%	$30,557,576	1
Communication Services	4.4%	$23,293,310	1
Real Estate	1.3%	$6,998,291	1

Last Quarter's Activity

Export CSV

Mar 31, 2026 vs Dec 31, 2025

Added To

Positions the filer increased

2 positions

Ticker	Company	Δ Shares	Shares	Value
ATS	ATS Corp /ATS	+840,602	16,404,170	$462,597,594
RC	Ready Capital Corp	+543,794	4,319,933	$6,998,291
No positions match the current search.

Trimmed

Positions the filer reduced

1 positions

Ticker	Company	Δ Shares	Shares	Value	Open
BKD	Brookdale Senior Living Inc.	−1,352,200	2,233,741	$30,557,576
No positions match the current search.

New Positions

Positions the filer opened this quarter

2 positions

Ticker	Company	Shares	Value
JELD	JELD-WEN Holding, Inc.	776,885	$963,337
NVRI	Enviri Corp	4,494,536	$0
No positions match the current search.

Sold Out

Positions the filer fully exited

4 positions

Ticker	Company	Shares	Value
SOLS	Solstice Advanced Materials Inc.	633,801	$30,790,052
JBS	Jbs N.V.	1,306,000	$18,832,520
BORR	Borr Drilling Ltd	2,182,136	$8,794,008
MLAB	Mesa Laboratories Inc /Co/	70,300	$5,518,550
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

6 tracked positions · $524,410,108 total · filing declares 7 positions · $612,852,905 · as of Mar 31, 2026

All sectors Communication Services Healthcare Industrials Real Estate

Ticker	Company	Type	Shares	Δ Shares	Value (USD)	% Δ Value	% of Portfolio
ATS	ATS Corp /ATS Industrials	Added	16,404,170	+840,602	$462,597,594	+7.9%	88.21%
BKD	Brookdale Senior Living Inc. Healthcare	Reduced	2,233,741	-1,352,200	$30,557,576	−21.0%	5.83%
CCO	Clear Channel Outdoor Holdings, Inc. Communication Services	Held	9,828,401	0	$23,293,310	+7.2%	4.44%
RC	Ready Capital Corp Real Estate	Added	4,319,933	+543,794	$6,998,291	−15.0%	1.33%
JELD	JELD-WEN Holding, Inc. Industrials	NEW	776,885	NEW	$963,337	NEW	0.18%
NVRI	Enviri Corp Industrials	NEW	4,494,536	NEW	$0	NEW	0.00%

Covers the securities this platform tracks: U.S.-listed common stock and the put/call positions reported on it. A 13F can also report security types outside that coverage — preferred shares, bonds, warrants, untracked share classes — so the filing's own declared total can exceed the figures above. The source filing is linked at the top of this table.