Top Institutional Investors

ACK Asset Management LLC — 13F Holdings & Portfolio

CIK 1510940 · latest 13F-HR filed 2026-08-13

Backtest portfolio

ACK Asset Management LLC manages $856.3M in 13F-reported U.S. long-equity assets across 21 reported positions as of its 2026-06-30 13F-HR filing. Its largest disclosed positions are WMS (7.15%), HLIO (7.10%), LFUS (6.65%). Quarter over quarter (versus its 2026-03-31 filing) the fund opened 7 new positions, exited 6, added to 10, and trimmed 3.

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.

Filer Information
Address
777 WEST PUTNAM AVENUE, SUITE 300
GREENWICH, CT 06830
Phone
(914) 220-8340
Filing Manager
ACK Asset Management LLC
GREENWICH, CT
Signatory
Andres Aguirre
CCO
Loading holdings…
AUM

$856.3M

Long-equity book

Holdings

21

Distinct positions

Period

2026-06-30

Filed 2026-08-13

Q/Q Activity

+7 / −6 / ↑10 / ↓3

vs 2026-03-31

Firm Profile & Key People
Name Title / Status Ownership Type

Top Adds (vs prior quarter)

  • EXP$18.2M +58.4%
  • JHX$15.2M +38.2%
  • CLFD$12.8M +65.7%
  • LFUS$11.1M +24.2%
  • HLIO$10.3M +20.4%
Show all 10 →

Top Trims

  • MTRN-$28.5M -41.5%
  • ATS-$8.9M -17.1%
  • SITE-$6.2M -14.0%
Show all 3 →

New Positions

  • GTX$54.3M
  • BWA$39.8M
  • DNOW$38.9M
  • ST$28.6M
  • SHLS$22.3M
Show all 7 →

Exited Positions

  • ROG$51.0M
  • NOVT$44.3M
  • DXPE$36.3M
  • CDNL$34.7M
  • GVA$30.0M
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 WMS WMS 00790R104 $61.2M 7.15% 390,000 SH
2 HLIO HLIO 42328H109 $60.8M 7.10% 681,000 SH
3 LFUS LFUS 537008104 $56.9M 6.65% 125,000 SH
4 JHX JHX G4253H101 $55.0M 6.42% 2,100,000 SH
5 GTX GTX 366505105 $54.3M 6.35% 1,500,000 SH
6 CNM CNM 21874C102 $52.6M 6.14% 1,090,000 SH
7 EXP EXP 26969P108 $49.5M 5.78% 220,000 SH
8 ATS ATS 00217Y104 $43.2M 5.04% 1,500,000 SH
9 ASTE ASTE 046224101 $42.2M 4.93% 690,276 SH
10 MTRN MTRN 576690101 $40.1M 4.69% 135,000 SH
11 BWA BWA 099724106 $39.8M 4.65% 600,000 SH
12 DNOW DNOW 67011P100 $38.9M 4.54% 3,000,000 SH
13 MBC MBC 57638P104 $38.1M 4.45% 3,700,000 SH
14 SITE SITE 82982L103 $37.8M 4.41% 330,000 SH
15 SWIM SWIM 51819L107 $36.6M 4.28% 5,660,000 SH
16 CLFD CLFD 18482P103 $32.2M 3.76% 810,200 SH
17 ST ST G8060N102 $28.6M 3.34% 600,000 SH
18 AERO-SWX — H55555108 $28.5M 3.32% 1,082,500 SH
19 SHLS SHLS 82489W107 $22.3M 2.61% 2,255,000 SH
20 EQPT EQPT 29445S100 $20.9M 2.44% 1,064,830 SH
21 MEI MEI 591520200 $16.6M 1.94% 877,500 SH
Filing History
Period Filed AUM Holdings Accession
2026-06-30 2026-08-13 $856.3M 21 0001510940-26-000005
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