SEC 13F Intelligence

Managers / Q1 2026

ACK Asset Management LLC

CIK 0001510940 · 777 WEST PUTNAM AVENUE, SUITE 300, GREENWICH, CT, 06830 · 914 220-8340

Reported Value
$801M
Q1 2026
Positions
20
Filings on Record
32
2019–present window
Filed
May 15, 2026
original filing

Summary

Ack Asset Management LLC reported $801M in U.S.-listed holdings across 20 positions for Q1 2026.

Its largest position, MTRN, represents 8.6% of the portfolio.

Compared with Q4 2025, the fund opened 3 new positions and exited 6.

Portfolio Metrics

Turnover
+23.9%
vs prior filed quarter
Top-10 Concentration
+62.0%
share of reported value
Largest Position
+8.6%
Mtrn
New / Exited
3 / 6
positions this quarter

Methodology: turnover is min(value bought, value sold) ÷ average reported value across the two quarters — value-based, so market moves inflate it slightly versus a share-based measure. Concentration and largest position are shares of the filing’s total reported value, options excluded. New/exited counts compare against the prior filed quarter. All figures derive solely from the fund’s 13F filings.

Reported Value by Quarter

13F Reported Value
Q4 ’18: $294.9BQ4 ’18Q1 ’19: $361.7BQ3 ’19: $356MQ4 ’19: $345MQ1 ’20: $200MQ1 ’20Q2 ’20: $221MQ3 ’20: $195MQ4 ’20: $243MQ1 ’21: $251MQ1 ’21Q2 ’21: $272MQ3 ’21: $342MQ4 ’21: $424MQ1 ’22: $461MQ1 ’22Q2 ’22: $357MQ3 ’22: $378MQ1 ’23: $655,113Q2 ’23: $802,904Q2 ’23Q3 ’23: $688,243Q1 ’24: $858MQ2 ’24: $810MQ3 ’24: $809MQ3 ’24Q4 ’24: $746MQ1 ’25: $609MQ2 ’25: $761MQ3 ’25: $799MQ3 ’25Q4 ’25: $797MQ1 ’26: $801Mfilingsflow.com

Portfolio Composition

By security type
Common Stock: 91.7%Other: 8.3%
  • Common Stock · 91.7% · $735M
  • Other · 8.3% · $67M

Quarter-over-Quarter Changes full breakdown →

vs Q4 2025 (amended baseline)

IssuerMoveShare ΔShares nowValue ΔValue now
LFUSLFUSNEW+135.0K135.0K+$46M$46M
CTSCTSNEW+584.0K584.0K+$28M$28M
SWIMSWIMNEW+5.16M5.16M+$28M$28M
AERO-SWXADDED+675.1K830.0K+$21M$27M
ENSENSSOLD OUT−304.3K0−$45M$0
ATROATROSOLD OUT−597.5K0−$32M$0
AINAINSOLD OUT−600.0K0−$30M$0
APOGAPOGSOLD OUT−813.0K0−$30M$0

Value changes conflate price moves with buying and selling — share changes are the real signal. Share counts are not split-adjusted.

Holdings — Q1 2026

20 positions
Export to Excel
#IssuerClass% PortfolioValue ↓Shares
1MTRNMTRNhistory →COM8.57%$69M474.8K
2WMSWMShistory →COM6.68%$53M390.0K
3ATSATShistory →COM6.50%$52M1.85M
4RG6ROGhistory →COM6.36%$51M475.0K
5HLIOHLIOhistory →COM6.30%$50M780.4K
6LFUSLFUShistory →COM5.72%$46M135.0K
7CNMCNMhistory →COM5.55%$44M900.0K
81GSNNOVThistory →COM5.53%$44M375.0K
9SITESITEhistory →COM5.48%$44M330.0K
10ASTEASTEhistory →COM5.29%$42M786.5K
11JHXCOM4.96%$40M2.10M
12DXPEDXPEhistory →COM4.53%$36M260.0K
13CDNLCDNLhistory →COM4.33%$35M874.0K
14EXPEXPhistory →COM3.90%$31M165.0K
15MBCMBChistory →COM3.84%$31M3.70M
16GVAGVAhistory →COM3.74%$30M250.0K
17CTSCTShistory →COM3.48%$28M584.0K
18SWIMSWIMhistory →COM3.46%$28M5.16M
19AERO-SWXCOM3.35%$27M830.0K
20CLFDCLFDhistory →COM2.43%$19M735.2K

Filing History

QuarterReported ValuePositionsFiledTypeLinks
Q1 2026$801M20May 15, 202613F-HRchanges · EDGAR ↗
Q4 2025$797M23Feb 13, 202613F-HRchanges · EDGAR ↗
Q3 2025$799M20Nov 14, 202513F-HRchanges · EDGAR ↗
Q2 2025$761M21Aug 13, 202513F-HRchanges · EDGAR ↗
Q1 2025$609M20May 13, 202513F-HRchanges · EDGAR ↗
Q4 2024$746M22Feb 13, 202513F-HRchanges · EDGAR ↗
Q3 2024$809M18Nov 13, 202413F-HRchanges · EDGAR ↗
Q2 2024$810M19Aug 13, 202413F-HRchanges · EDGAR ↗
Q1 2024$858M20May 14, 202413F-HRchanges · EDGAR ↗
Q4 2023Under review21Feb 13, 202413F-HRchanges · EDGAR ↗
Q3 2023$688,24321Nov 13, 202313F-HRchanges · EDGAR ↗
Q2 2023$802,90423Aug 15, 2023RESTATEMENTchanges · EDGAR ↗
Q1 2023$655,11323May 12, 202313F-HRchanges · EDGAR ↗
Q4 2022Under review25Feb 14, 202313F-HRchanges · EDGAR ↗
Q3 2022$378M23Nov 14, 202213F-HRchanges · EDGAR ↗
Q2 2022$357M21Aug 15, 202213F-HRchanges · EDGAR ↗
Q1 2022$461M24May 13, 202213F-HRchanges · EDGAR ↗
Q4 2021$424M27Feb 14, 202213F-HRchanges · EDGAR ↗
Q3 2021$342M26Nov 12, 202113F-HRchanges · EDGAR ↗
Q2 2021$272M24Jul 13, 202113F-HRchanges · EDGAR ↗
Q1 2021$251M23May 14, 202113F-HRchanges · EDGAR ↗
Q4 2020$243M28Feb 12, 202113F-HRchanges · EDGAR ↗
Q3 2020$195M19Nov 13, 202013F-HRchanges · EDGAR ↗
Q2 2020$221M20Aug 13, 202013F-HRchanges · EDGAR ↗
Q1 2020$200M20May 14, 202013F-HRchanges · EDGAR ↗
Q4 2019$345M23Feb 12, 202013F-HRchanges · EDGAR ↗
Q3 2019$356M25Nov 13, 2019RESTATEMENTchanges · EDGAR ↗
Q2 2019Under review26Aug 14, 201913F-HRchanges · EDGAR ↗
Q1 2019$361.7B30May 13, 201913F-HRchanges · EDGAR ↗
Q4 2018$294.9B29Feb 12, 201913F-HRchanges · EDGAR ↗

13F filings are due up to 45 days after quarter end, so holdings shown here lag the fund’s current book. Source: original SEC filing on EDGAR ↗.