ACK Asset Management LLC 13F holdings
ACK Asset Management LLC reported 21 positions with a total reported value of $856.3M as of 2026-06-30, in its 13F for Q2 2026, filed 2026-08-13. Top holdings by reported value: WMS (7.1%), HLIO HLIO (7.1%), LFUS LFUS (6.6%), JHX JHX (6.4%), GTX GTX (6.3%). Against 2026-03-31 it opened 7 new positions and exited 6. Next 13F due by 2026-11-14, the legal deadline 45 days after the quarter ending 2026-09-30.
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Top holdings
21 largest of 21 positions · reported value as of 2026-06-30
| Holding | Shares | Reported value | % of portfolio |
|---|---|---|---|
| WMS | 390,000 | $61.2M | 7.1% |
| HLIO HLIO | 681,000 | $60.8M | 7.1% |
| LFUS LFUS | 125,000 | $56.9M | 6.6% |
| JHX JHX | 2,100,000 | $55.0M | 6.4% |
| GTX GTX | 1,500,000 | $54.3M | 6.3% |
| CNM CNM | 1,090,000 | $52.6M | 6.1% |
| EXP | 220,000 | $49.5M | 5.8% |
| ATS ATS | 1,500,000 | $43.2M | 5.0% |
| ASTE | 690,276 | $42.2M | 4.9% |
| MTRN MTRN | 135,000 | $40.1M | 4.7% |
| BWA BWA | 600,000 | $39.8M | 4.7% |
| DNOW DNOW | 3,000,000 | $38.9M | 4.5% |
| MBC MBC | 3,700,000 | $38.1M | 4.4% |
| SITE SITE | 330,000 | $37.8M | 4.4% |
| SWIM SWIM | 5,660,000 | $36.6M | 4.3% |
| CLFD CLFD | 810,200 | $32.2M | 3.8% |
| ST ST | 600,000 | $28.6M | 3.3% |
| AERO-SWX | 1,082,500 | $28.5M | 3.3% |
| SHLS SHLS | 2,255,000 | $22.3M | 2.6% |
| EQPT EQPT | 1,064,830 | $20.9M | 2.4% |
| MEI | 877,500 | $16.6M | 1.9% |
SEC FORM 13F · Q2 2026 · VALUES AS REPORTED, NOT PRICES
New positions this quarter
Held at 2026-06-30, not at 2026-03-31 · 7 in all · reported value as of 2026-06-30
Sold out
Held at 2026-03-31, gone by 2026-06-30 · 6 in all · reported value as of 2026-03-31
Biggest increases and decreases
Positions held at both quarter ends, by change in shares · reported value as of 2026-06-30
Increases
| Holding | Shares 2026-03-31 | Shares 2026-06-30 | Change | Reported value |
|---|---|---|---|---|
| EXP | 165,000 | 220,000 | +33.3% | $49.5M |
| CNM CNM | 900,000 | 1,090,000 | +21.1% | $52.6M |
| AERO-SWX | 830,000 | 1,082,500 | +30.4% | $28.5M |
| SWIM SWIM | 5,160,000 | 5,660,000 | +9.7% | $36.6M |
| CLFD CLFD | 735,200 | 810,200 | +10.2% | $32.2M |
Decreases
| Holding | Shares 2026-03-31 | Shares 2026-06-30 | Change | Reported value |
|---|---|---|---|---|
| MTRN MTRN | 474,800 | 135,000 | -71.6% | $40.1M |
| ATS ATS | 1,846,196 | 1,500,000 | -18.8% | $43.2M |
| HLIO HLIO | 780,378 | 681,000 | -12.7% | $60.8M |
| ASTE | 786,500 | 690,276 | -12.2% | $42.2M |
| LFUS LFUS | 135,000 | 125,000 | -7.4% | $56.9M |
CIK 1510940 · 13F FILINGS ON EDGAR · INFORMATIONAL ONLY
