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ACK Asset Management LLC — 13F Holdings & Portfolio

CIK 1510940 · latest 13F-HR filed 2026-05-15

Backtest portfolio

ACK Asset Management LLC manages $801.1M in 13F-reported U.S. long-equity assets across 20 reported positions as of its 2026-03-31 13F-HR filing. Its largest disclosed positions are MTRN (8.57%), WMS (6.68%), ATS (6.50%). Quarter over quarter (versus its 2025-12-31 filing) the fund opened 3 new positions, exited 6, added to 10, and trimmed 4.

AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.

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AUM

$801.1M

Long-equity book

Holdings

20

Distinct positions

Period

2026-03-31

Filed 2026-05-15

Q/Q Activity

+3 / −6 / ↑10 / ↓4

vs 2025-12-31

Firm Profile & Key People
Name Title / Status Ownership Type

Top Adds (vs prior quarter)

  • AERO-SWX$21.3M +385.0%
  • CDNL$14.2M +69.7%
  • ROG$11.0M +27.5%
  • DXPE$10.0M +37.9%
  • MTRN$9.7M +16.4%
Show all 10 →

Top Trims

  • GVA-$27.7M -48.0%
  • JHX-$3.8M -8.7%
  • WMS-$3.0M -5.3%
  • EXP-$2.8M -8.3%
Show all 4 →

New Positions

  • LFUS$45.8M
  • CTS$27.9M
  • SWIM$27.7M
Show all 3 →

Exited Positions

  • ENS$44.7M
  • ATRO$32.4M
  • AIN$30.4M
  • APOG$29.6M
  • ERII$9.1M
Show all 6 →
All Holdings

Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).

# Issuer Symbol CUSIP Value Weight Shares Type
1 MTRN MTRN 576690101 $68.7M 8.57% 474,800 SH
2 WMS WMS 00790R104 $53.5M 6.68% 390,000 SH
3 ATS ATS 00217Y104 $52.1M 6.50% 1,846,196 SH
4 ROG ROG 775133101 $51.0M 6.36% 475,000 SH
5 HLIO HLIO 42328H109 $50.5M 6.30% 780,378 SH
6 LFUS LFUS 537008104 $45.8M 5.72% 135,000 SH
7 CNM CNM 21874C102 $44.5M 5.55% 900,000 SH
8 NOVT NOVT 67000B104 $44.3M 5.53% 375,000 SH
9 SITE SITE 82982L103 $43.9M 5.48% 330,000 SH
10 ASTE ASTE 046224101 $42.3M 5.29% 786,500 SH
11 JHX JHX G4253H101 $39.8M 4.96% 2,100,000 SH
12 DXPE DXPE 233377407 $36.3M 4.53% 260,000 SH
13 CDNL CDNL 14154A102 $34.7M 4.33% 874,000 SH
14 EXP EXP 26969P108 $31.3M 3.90% 165,000 SH
15 MBC MBC 57638P104 $30.7M 3.84% 3,700,000 SH
16 GVA GVA 387328107 $30.0M 3.74% 250,000 SH
17 CTS CTS 126501105 $27.9M 3.48% 584,000 SH
18 SWIM SWIM 51819L107 $27.7M 3.46% 5,160,000 SH
19 AERO-SWX — H55555108 $26.8M 3.35% 830,000 SH
20 CLFD CLFD 18482P103 $19.5M 2.43% 735,200 SH
Filing History
Period Filed AUM Holdings Accession
2026-03-31 2026-05-15 $801.1M 20 0001510940-26-000004
2025-12-31 2026-02-13 $796.8M 23 0001510940-26-000001
2025-09-30 2025-11-14 $799.1M 20 0001510940-25-000006