ACK Asset Management LLC — 13F Holdings & Portfolio
CIK 1510940 · latest 13F-HR filed 2026-08-13
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 and exited 6; 10 existing positions rose in reported value and 3 fell.
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.
Long-equity book
Distinct positions
Filed 2026-08-13
vs 2026-03-31
Portfolio charts
Latest quarter's book, what changed, and how the portfolio has evolved across filings.
Portfolio map
Q2 26Box size = position value; colour = change in share count vs the prior quarter (green added, red trimmed, blue new). Rows split across managers or share classes are combined. Click a box for the stock.
Sector mix
% of 13F valueSectors from each company's SIC code; funds and ETFs grouped separately.
Biggest buys and sells
Q1 26 → Q2 26Estimated from the change in shares held × the quarter-end price, so price moves alone don't count as buying. New and exited positions are included.
13F assets and positions
4 quartersTotal reported 13F value (bars) and number of positions (line) each quarter. Value changes include market moves.
Top positions over time
reported valueThe eight largest current positions, valued at each quarter end.
Concentration
top 10 = 60.2%Cumulative share of the portfolio held in the largest N positions.
As of the firm’s regulatory filing dated Mar 13, 2026.
SUITE 300
GREENWICH, CT 06830
| Name | Title / Status | Ownership | Type |
|---|---|---|---|
| AGUIRRE, ANDRES, MAURICIO Control | CHIEF COMPLIANCE OFFICER & SENIOR CONTROLLER since Jan 2023 | Less than 5% | Individual |
| COOPER, KENNETH, FRANK Control | CHIEF FINANCIAL OFFICER since Oct 2010 | Less than 5% | Individual |
| KISSELL, WILLIAM, ANDREW Control | OFFICER since Oct 2010 | Less than 5% | Individual |
| MEISENBERG, RICHARD, SCOTT Control | MANAGING MEMBER since Oct 2005 | 50–75% | Individual |
| REILLY, JOHN, HENRY Control | MANAGING MEMBER since Oct 2005 | 25–50% | Individual |
| KERR, GORDON, CHARLES | CHIEF OPERATING OFFICER since Jan 2025 | Less than 5% | Individual |
Ownership & leadership changes · 5 filings with changes since Jan 30, 2012
From the firm’s regulatory filings, newest first. Dates are filing dates: a filing that no longer lists someone does not say when they left.
- AddedKERR, GORDON, CHARLES · CHIEF OPERATING OFFICER · Less than 5%
- AddedAGUIRRE, ANDRES, MAURICIO · CHIEF COMPLIANCE OFFICER & SENIOR CONTROLLER · Less than 5% · control person
- ChangedCOOPER, KENNETH, FRANK · title CHIEF FINANCIAL OFFICER AND CHIEF COMPLIANCE OFFICER → CHIEF FINANCIAL OFFICER
- ChangedMEISENBERG, RICHARD, SCOTT · title MANAGING MEMBER / MANAGING MEMBER (GENERAL PARTNER) → MANAGING MEMBER
- ChangedREILLY, JOHN, HENRY · title MANAGING MEMBER / MANAGING MEMBER (GENERAL PARTNER) → MANAGING MEMBER
- AddedKISSELL, WILLIAM, ANDREW · OFFICER · Less than 5% · control person
- ChangedMEISENBERG, RICHARD, SCOTT · title MANAGING MEMBER → MANAGING MEMBER / MANAGING MEMBER (GENERAL PARTNER)
- ChangedREILLY, JOHN, HENRY · title MANAGING MEMBER → MANAGING MEMBER / MANAGING MEMBER (GENERAL PARTNER)
- ListedCOOPER, KENNETH, FRANK · CHIEF FINANCIAL OFFICER AND CHIEF COMPLIANCE OFFICER · Less than 5% · control person
- ListedMEISENBERG, RICHARD, SCOTT · MANAGING MEMBER · 50–75% · control person
- ListedREILLY, JOHN, HENRY · MANAGING MEMBER · 25–50% · control person
Quarter-over-quarter changes
Changes in reported position value vs the prior 13F, so price moves count too, not just shares bought or sold.
ACK Asset Management LLC Holdings (2026-06-30)
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 |
| 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 |
GREENWICH, CT 06830