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ACK Asset Management LLC

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13F filer, CIK 1510940, GREENWICH, CT

ACK Asset Management LLC reported $761,426,347 across 21 holdings for the quarter ended 2025-06-30, in a 13F-HR filed 2025-08-13. Its ten largest share positions make up 65.98% of the portfolio.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001510940-25-000005

Period
2025-06-30
Reported value
$761M
Holdings
21
Top 10 weight
65.98%
New
6
Sold out
5

Largest buys vs the previous quarter

SecurityShares changeApprox. value
AINnew+585,000$41M
RRXnew+275,000$39.9M
WMSnew+345,000$39.6M
GVAadded+354,300$33.1M
CTRIadded+811,409$18.2M

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Largest sells vs the previous quarter

SecurityShares changeApprox. value
MTZreduced-337,700-$57.6M
DYreduced-158,100-$38.6M
ROGexited-517,500-$34.9M
CECOexited-1,201,000-$27.4M
MBCexited-1,302,500-$17M

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Holdings, Q2 2025

Share positions as resolved from 13F-HR 0001510940-25-000005, largest first. % of portfolio is the value over $761,426,347, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
ATROASTRONICS CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,060,000 shares; 2024Q4: 2,060,000 shares; 2025Q1: 2,060,000 shares; 2025Q2: 2,060,000 shares 2,060,000$69M9.06%0Timeline
ATSATS CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,255,889 shares; 2024Q4: 2,093,196 shares; 2025Q1: 2,013,196 shares; 2025Q2: 1,846,196 shares 1,846,196$58.9M7.73%-167,000Timeline
DYDYCOM INDS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 535,500 shares; 2024Q4: 445,500 shares; 2025Q1: 382,800 shares; 2025Q2: 224,700 shares 224,700$54.9M7.21%-158,100Timeline
GVAGRANITE CONSTR INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 825,000 shares; 2024Q4: 284,000 shares; 2025Q1: 190,700 shares; 2025Q2: 545,000 shares 545,000$51M6.69%+354,300Timeline
ENSENERSYSQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 715,000 shares; 2024Q4: 671,024 shares; 2025Q1: 624,324 shares; 2025Q2: 584,324 shares 584,324$50.1M6.58%-40,000Timeline
MYRGMYR GROUP INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 200,000 shares; 2025Q1: 279,100 shares; 2025Q2: 265,200 shares 265,200$48.1M6.32%-13,900Timeline
CTRICENTURI HOLDINGS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 1,300,000 shares; 2025Q1: 1,220,591 shares; 2025Q2: 2,032,000 shares 2,032,000$45.6M5.99%+811,409Timeline
JBTMJBT MAREL CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 400,000 shares; 2025Q1: 369,800 shares; 2025Q2: 350,546 shares 350,546$42.2M5.54%-19,254Timeline
MTRNMATERION CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 505,500 shares; 2024Q4: 494,800 shares; 2025Q1: 459,200 shares; 2025Q2: 524,800 shares 524,800$41.7M5.47%+65,600Timeline
AINALBANY INTL CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 585,000 shares 585,000$41M5.39%newTimeline
RRXREGAL REXNORD CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 275,000 shares 275,000$39.9M5.24%newTimeline
WMSADVANCED DRAIN SYS INC DELQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 345,000 shares 345,000$39.6M5.2%newTimeline
MRC GLOBAL INCMRC GLOBAL INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 550,000 shares; 2025Q1: 1,565,000 shares; 2025Q2: 2,267,000 shares 2,267,000$31.1M4.08%+702,000
SITESITEONE LANDSCAPE SUPPLY INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: 100,000 shares; 2025Q2: 250,000 shares 250,000$30.2M3.97%+150,000Timeline
MIRMIRION TECHNOLOGIES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 4,246,300 shares; 2024Q4: 1,815,000 shares; 2025Q1: 1,618,356 shares; 2025Q2: 1,337,000 shares 1,337,000$28.8M3.78%-281,356Timeline
CLFDCLEARFIELD INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 695,000 shares; 2024Q4: 720,000 shares; 2025Q1: 687,200 shares; 2025Q2: 625,200 shares 625,200$27.1M3.56%-62,000Timeline
MTZMASTEC INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 772,300 shares; 2024Q4: 531,800 shares; 2025Q1: 462,700 shares; 2025Q2: 125,000 shares 125,000$21.3M2.8%-337,700Timeline
MTRXMATRIX SVC COQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 801,000 shares; 2024Q4: 1,179,901 shares; 2025Q1: 1,184,100 shares; 2025Q2: 1,087,100 shares 1,087,100$14.7M1.93%-97,000Timeline
NPKINPK INTERNATIONAL INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 1,226,808 shares 1,226,808$10.4M1.37%newTimeline
CTOSCUSTOM TRUCK ONE SOURCE INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 1,875,000 shares 1,875,000$9.26M1.22%newTimeline
DXPEDXP ENTERPRISES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q3: restricted; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 75,600 shares 75,600$6.63M0.87%newTimeline

Sold out in Q2 2025

Positions in the previous quarter's report that this quarter's report no longer lists.

SecurityShares beforeValue beforeType
ROGROGERS CORP517,500$34.9Mshares
CECOCECO ENVIRONMENTAL CORP1,201,000$27.4Mshares
MBCMASTERBRAND INC1,302,500$17Mshares
BIRDFBIRD CONSTRUCTION INC. COMMON1,120,800$17Mshares
LASRNLIGHT INC754,000$5.86Mshares

How Q2 2025 was built

Available 13F filings of this filer for the quarter and their roles: the base report is the latest original or restatement, NEW HOLDINGS amendments filed after it are added (method).

FilingRoleAmendmentFiledAcceptedIngested
13F-HR 0001510940-25-000005 base2025-08-13acceptance time not in the bulk data set