ACK Asset Management LLC
In its 13F for Q2 2026 (holdings as of June 30, 2026, filed August 13, 2026), ACK Asset Management LLC reported 21 stock positions worth $856.3 million. Its top holding was Advanced Drainage Systems (WMS) at 7.1% of the portfolio, followed by Helios Technologies (HLIO, 7.1%) and Littelfuse (LFUS, 6.6%). Compared with Q1 2026, it opened 7 new positions, sold out of 6, added to 5 and reduced 5. The biggest buy was a new position in Garrett Motion (GTX) and the biggest sale an exit from Rogers (ROG).
- Most Recent 13F
- Q2 2026
- Location
- GREENWICH, CT
- CIK
- 0001510940
- Portfolio Value
- $856.3M (Q2 2026)
- SEC Filing
- 0001510940-26-000005 ↗ filed Aug 13, 2026
Holdings Value
Holdings 21 stocks · $856.3M
| WMS Advanced Drainage Systems Inc. | 7.15% | 390,000 | $61.2M | No change |
| HLIO Helios Technologies Inc. | 7.10% | 681,000 | $60.8M | Reduce -12.7% |
| LFUS Littelfuse Inc. | 6.65% | 125,000 | $56.9M | Reduce -7.4% |
| JHX James Hardie Ind PLC | 6.42% | 2,100,000 | $55.0M | No change |
| GTX Garrett Motion Inc. | 6.35% | 1,500,000 | $54.3M | New |
| CNM Core & Main Inc. Class A | 6.14% | 1,090,000 | $52.6M | Add +21.1% |
| EXP Eagle Materials Inc. | 5.78% | 220,000 | $49.5M | Add +33.3% |
| ATS Ats Corp. | 5.04% | 1,500,000 | $43.2M | Reduce -18.8% |
| ASTE Astec Industries Inc. | 4.93% | 690,276 | $42.2M | Reduce -12.2% |
| MTRN Materion Corp. | 4.69% | 135,000 | $40.1M | Reduce -71.6% |
| BWA Borgwarner Inc. | 4.65% | 600,000 | $39.8M | New |
| DNOW Dnow Inc. | 4.54% | 3,000,000 | $38.9M | New |
| MBC Masterbrand Inc. | 4.45% | 3,700,000 | $38.1M | No change |
| SITE Siteone Landscape Supply Inc. | 4.41% | 330,000 | $37.8M | No change |
| SWIM Latham Group Inc. | 4.28% | 5,660,000 | $36.6M | Add +9.7% |
| CLFD Clearfield Inc. | 3.76% | 810,200 | $32.2M | Add +10.2% |
| ST Sensata Technologies Holdplc | 3.35% | 600,000 | $28.6M | New |
| MTASF Montana Aerospace AG filed as AERO-SWX | 3.32% | 1,082,500 | $28.5M | Add +30.4% |
| SHLS Shoals Technologies Group -A | 2.61% | 2,255,000 | $22.3M | New |
| EQPT Equipmentshare.com Inc. Class A | 2.44% | 1,064,830 | $20.9M | New |
| MEI Methode Electronics Inc. | 1.94% | 877,500 | $16.6M | New |
Portfolio Sells Q1 2026 → Q2 2026
| ROG Rogers Corp. | Sold out | 0.00% | −6.36 |
| NOVT Novanta Inc. | Sold out | 0.00% | −5.53 |
| DXPE DXP Enterprises Inc. | Sold out | 0.00% | −4.53 |
| CDNL Cardinal Infrastructure GR-A | Sold out | 0.00% | −4.33 |
| MTRN Materion Corp. | Reduce -71.6% | 4.69% | −3.88 |
| GVA Granite Construction Inc. | Sold out | 0.00% | −3.74 |
| CTS CTS Corp. | Sold out | 0.00% | −3.48 |
| ATS Ats Corp. | Reduce -18.8% | 5.04% | −1.46 |
| ASTE Astec Industries Inc. | Reduce -12.2% | 4.93% | −0.35 |
| HLIO Helios Technologies Inc. | Reduce -12.7% | 7.10% | +0.79 |
| LFUS Littelfuse Inc. | Reduce -7.4% | 6.65% | +0.93 |
Portfolio Buys Q1 2026 → Q2 2026
| GTX Garrett Motion Inc. | New | 6.35% | +6.35 |
| BWA Borgwarner Inc. | New | 4.65% | +4.65 |
| DNOW Dnow Inc. | New | 4.54% | +4.54 |
| ST Sensata Technologies Holdplc | New | 3.35% | +3.35 |
| SHLS Shoals Technologies Group -A | New | 2.61% | +2.61 |
| EQPT Equipmentshare.com Inc. Class A | New | 2.44% | +2.44 |
| MEI Methode Electronics Inc. | New | 1.94% | +1.94 |
| EXP Eagle Materials Inc. | Add +33.3% | 5.78% | +1.88 |
| CLFD Clearfield Inc. | Add +10.2% | 3.76% | +1.34 |
| SWIM Latham Group Inc. | Add +9.7% | 4.28% | +0.82 |
| CNM Core & Main Inc. Class A | Add +21.1% | 6.14% | +0.59 |
| MTASF Montana Aerospace AG | Add +30.4% | 3.32% | −0.02 |
All Filings
| Quarter | Positions | 13F Reported Value | Top Holdings |
|---|---|---|---|
| Q2 2026 | 21 | $856.3M | WMS, HLIO, LFUS, JHX, GTX |
| Q1 2026 | 20 | $801.1M | MTRN, WMS, ATS, ROG, HLIO |
| Q4 2025 | 23 | $796.8M | MTRN, GVA, WMS, ATS, CNM |
| Q3 2025 | 20 | $799.1M | ENS, MTRN, GVA, ATRO, WMS |
| Q2 2025 | 21 | $761.4M | ATRO, ATS, DY, GVA, ENS |
| Q1 2025 | 20 | $609.0M | DY, ENS, MTZ, ATS, ATRO |
| Q4 2024 | 22 | $746.4M | DY, MTZ, ATS, ENS, ROG |
| Q3 2024 | 18 | $809.2M | DY, MTZ, ENS, ROG, ATS |
| Q2 2024 | 19 | $810.3M | DY, MTZ, ENS, ROG, CNM |
| Q1 2024 | 20 | $858.3M | CNM, DY, ATKR, MTZ, ENS |