ACK Asset Management LLC holds a focused book of 21 reported positions worth $856.3M as of Q2 2026 (disclosed Aug 13, 2026, a ~44-day 13F lag). This quarter they opened Garrett Motion Inc and trimmed Helios Technologies Inc. Their largest long position is Advanced Drainage Systems In at 7% of the reported non-option book. Cloning the disclosed picks since 2013 would be +649% (+17.0%/yr). That is a simulation of the disclosed long book, not audited returns.
The reported book (valued from quarter-end) returned +731.9%, a 82.8-point gap that is the cost of the ~44-day 13F disclosure lag a real follower can't avoid.
Growth of $10,000 cloning ACK Asset Management LLC's disclosed long 13F book, rebalanced on each filing date (so it reflects each quarter's actual reporting lag, ~44 days for the latest filing, with no look-ahead), total-return basis (dividends reinvested), derived from end-of-day prices. “Their reported book” values the same picks from quarter-end, before they were public. S&P 500 is SPY total return over the same window. Excludes shorts, cash, options and non-13F holdings. Not investment advice.
Top-heavy: focused book
Share of the disclosed book in its largest positions. A higher top-5 share means a more concentrated, higher-conviction portfolio.
97% mapped to company sectors
Direct operating-company sectors from our SIC-based security master. ETF/fund and unclassified holdings stay visible separately; this is not ETF look-through exposure.
Estimated $ traded · quarter-end prices (an exit at the prior quarter-end), no cost basis
Other tracked managers holding the same core names as ACK Asset Management LLC
| Manager / fund | Shared names | Their $ in those |
|---|---|---|
| Gem Investment Advisors, LLC | 2 / 21 | $36.3M |
| Harvey Partners, LLC | 4 / 21 | $174.4M |
| Hill City Capital, LP | 8 / 21 | $448.7M |
| Congruence Capital, LLC | 2 / 21 | $31.6M |
| Towle & Co | 2 / 21 | $19.5M |
| Diameter Capital Partners LP | 2 / 21 | $79.9M |
| Formula Growth Ltd | 3 / 21 | $18.1M |
| Roubaix Capital, LLC | 3 / 21 | $16.8M |
Ranked by the share of each fund's own book sitting in the names it shares with ACK Asset Management LLC: only funds sharing at least a tenth of the book qualify. Index giants, bank custody books and market makers are excluded. They hold everything, so their overlap says nothing.
Bars show each position's share of the portfolio. Click a row for its position history.
| # | Security | Value | Shares | % Port | Last move | History |
|---|---|---|---|---|---|---|
| 1 | WMS COM | $61.2M | 390.0K | 7.1% | —Held | |
| 2 | HLIO COM | $60.8M | 681.0K | 7.1% | ▼−13% Reduced · −99K sh | |
| 3 | LFUS COM | $56.9M | 125.0K | 6.6% | ▼−7.4% Reduced · −10K sh | |
| 4 | JHX COM | $55.0M | 2.10M | 6.4% | —Held | |
| 5 | GTX COM | $54.3M | 1.50M | 6.3% | ▲New New position | |
| 6 | CNM COM | $52.6M | 1.09M | 6.1% | ▲+21% Added · +190K sh | |
| 7 | EXP COM | $49.5M | 220.0K | 5.8% | ▲+33% Added · +55K sh | |
| 8 | ATS COM | $43.2M | 1.50M | 5.0% | ▼−19% Reduced · −346K sh | |
| 9 | ASTE COM | $42.2M | 690.3K | 4.9% | ▼−12% Reduced · −96K sh | |
| 10 | MTRN COM | $40.1M | 135.0K | 4.7% | ▼−72% Reduced · −340K sh | |
| 11 | BWA COM | $39.8M | 600.0K | 4.7% | ▲New New position | |
| 12 | DNOW COM | $38.9M | 3.00M | 4.5% | ▲New New position | |
| 13 | MBC COM | $38.1M | 3.70M | 4.4% | —Held | |
| 14 | SITE COM | $37.8M | 330.0K | 4.4% | —Held | |
| 15 | SWIM COM | $36.6M | 5.66M | 4.3% | ▲+9.7% Added · +500K sh | |
| 16 | CLFD COM | $32.2M | 810.2K | 3.8% | ▲+10% Added · +75K sh | |
| 17 | ST COM | $28.6M | 600.0K | 3.3% | ▲New New position | |
| 18 | Aero-SWX COM | $28.5M | 1.08M | 3.3% | ▲+30% Added · +253K sh | |
| 19 | SHLS COM | $22.3M | 2.25M | 2.6% | ▲New New position | |
| 20 | EQPT COM | $20.9M | 1.06M | 2.4% | ▲New New position | |
| 21 | MEI COM | $16.6M | 877.5K | 1.9% | ▲New New position |
This fund page is the Follow view. The Build view lets your agent pull holdings, quarter changes, overlap, and source filings through API or MCP.
curl -H "Authorization: Bearer YOUR_API_KEY" \ "https://arkolith.com/api/v1/funds/1510940/holdings"
Use Arkolith to show ACK Asset Management LLC's latest holdings, largest changes, and filing provenance.
As-of date vs the date the SEC received each filing
Reported 13F total per quarter. Raw filing totals can include option notional.
| Quarter | As of | Filed | Lag | Positions | Value | Form |
|---|---|---|---|---|---|---|
| Q2 2026 | Jun 30, 2026 | Aug 13, 2026 | 44d | 21 | $856.3M | 13F-HR |
| Q1 2026 | Mar 31, 2026 | May 15, 2026 | 45d | 20 | $801.1M | 13F-HR |
| Q4 2025 | Dec 31, 2025 | Feb 13, 2026 | 44d | 23 | $796.8M | 13F-HR |
| Q3 2025 | Sep 30, 2025 | Nov 14, 2025 | 45d | 20 | $799.1M | 13F-HR |
| Q2 2025 | Jun 30, 2025 | Aug 13, 2025 | 44d | 21 | $761.4M | 13F-HR |
| Q1 2025 | Mar 31, 2025 | May 13, 2025 | 43d | 20 | $609.0M | 13F-HR |
| Q4 2024 | Dec 31, 2024 | Feb 13, 2025 | 44d | 22 | $746.4M | 13F-HR |
| Q3 2024 | Sep 30, 2024 | Nov 13, 2024 | 44d | 18 | $809.2M | 13F-HR |
| Q2 2024 | Jun 30, 2024 | Aug 13, 2024 | 44d | 19 | $810.3M | 13F-HR |
| Q1 2024 | Mar 31, 2024 | May 14, 2024 | 44d | 20 | $858.3M | 13F-HR |
| Q4 2023 | Dec 31, 2023 | Feb 13, 2024 | 44d | 21 | $831.3M | 13F-HR |
| Q3 2023 | Sep 30, 2023 | Nov 13, 2023 | 44d | 21 | $688.2M | 13F-HR |
| Q2 2023 | Jun 30, 2023 | Aug 15, 2023 | 46d | 23 | $802.9M | 13F-HR/A |
| Q1 2023 | Mar 31, 2023 | May 12, 2023 | 42d | 23 | $655.1M | 13F-HR |
| Q4 2022 | Dec 31, 2022 | Feb 14, 2023 | 45d | 25 | $544.6M | 13F-HR |
| Q3 2022 | Sep 30, 2022 | Nov 14, 2022 | 45d | 23 | $377.5M | 13F-HR |
| Q2 2022 | Jun 30, 2022 | Aug 15, 2022 | 46d | 21 | $357.3M | 13F-HR |
| Q1 2022 | Mar 31, 2022 | May 13, 2022 | 43d | 24 | $461.0M | 13F-HR |
| Q4 2021 | Dec 31, 2021 | Feb 14, 2022 | 45d | 27 | $423.9M | 13F-HR |
| Q3 2021 | Sep 30, 2021 | Nov 12, 2021 | 43d | 26 | $341.6M | 13F-HR |
| Q2 2021 | Jun 30, 2021 | Jul 13, 2021 | 13d | 24 | $271.7M | 13F-HR |
| Q1 2021 | Mar 31, 2021 | May 14, 2021 | 44d | 23 | $251.4M | 13F-HR |
| Q4 2020 | Dec 31, 2020 | Feb 12, 2021 | 43d | 28 | $242.9M | 13F-HR |
Holdings from SEC EDGAR 13F-HR filings, updated quarterly, filed up to 45 days after quarter-end. Public domain. Book totals and portfolio weights cover reported non-option positions, which can include notes and warrants. Disclosed put/call options are listed separately and excluded from those totals. The performance line is a simulation of the disclosed long book, not an audited return.