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ACK Asset Management LLC

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13F filer, CIK 1510940, GREENWICH, CT

ACK Asset Management LLC reported $799,134,177 across 20 holdings for the quarter ended 2025-09-30, in a 13F-HR filed 2025-11-14. Its ten largest share positions make up 65.85% of the portfolio.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001510940-25-000006

Period
2025-09-30
Reported value
$799M
Holdings
20
Top 10 weight
65.85%
New
7
Sold out
8

Largest buys vs the previous quarter

SecurityShares changeApprox. value
CNMnew+900,000$48.4M
JHXnew+2,100,000$40.3M
HLIOnew+770,000$40.1M
ASTEnew+701,500$33.8M
APOGnew+708,000$30.8M

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
DYexited-224,700-$54.9M
MYRGexited-265,200-$48.1M
RRXexited-275,000-$39.9M
ATROreduced-830,000-$37.9M
MRC GLOBAL INCexited-2,267,000-$31.1M

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, Q3 2025

Share positions as resolved from 13F-HR 0001510940-25-000006, largest first. % of portfolio is the value over $799,134,177, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
ENSENERSYSQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 715,000 shares; 2024Q4: 671,024 shares; 2025Q1: 624,324 shares; 2025Q2: 584,324 shares; 2025Q3: 584,324 shares 584,324$66M8.26%0Timeline
MTRNMATERION CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 505,500 shares; 2024Q4: 494,800 shares; 2025Q1: 459,200 shares; 2025Q2: 524,800 shares; 2025Q3: 524,800 shares 524,800$63.4M7.93%0Timeline
GVAGRANITE CONSTR INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 825,000 shares; 2024Q4: 284,000 shares; 2025Q1: 190,700 shares; 2025Q2: 545,000 shares; 2025Q3: 545,000 shares 545,000$59.8M7.48%0Timeline
ATROASTRONICS CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 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; 2025Q3: 1,230,000 shares 1,230,000$56.1M7.02%-830,000Timeline
WMSADVANCED DRAIN SYS INC DELQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 345,000 shares; 2025Q3: 390,000 shares 390,000$54.1M6.77%+45,000Timeline
JBTMJBT MAREL CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 400,000 shares; 2025Q1: 369,800 shares; 2025Q2: 350,546 shares; 2025Q3: 350,546 shares 350,546$49.2M6.16%0Timeline
CNMCORE & MAIN INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 900,000 shares 900,000$48.4M6.06%newTimeline
ATSATS CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 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; 2025Q3: 1,846,196 shares 1,846,196$48.4M6.05%0Timeline
AINALBANY INTL CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 585,000 shares; 2025Q3: 760,000 shares 760,000$40.5M5.07%+175,000Timeline
JHXJAMES HARDIE INDS PLCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 2,100,000 shares 2,100,000$40.3M5.05%newTimeline
HLIOHELIOS TECHNOLOGIES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 770,000 shares 770,000$40.1M5.02%newTimeline
SITESITEONE LANDSCAPE SUPPLY INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: 100,000 shares; 2025Q2: 250,000 shares; 2025Q3: 280,000 shares 280,000$36.1M4.51%+30,000Timeline
ASTEASTEC INDS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 701,500 shares 701,500$33.8M4.22%newTimeline
APOGAPOGEE ENTERPRISES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 708,000 shares 708,000$30.8M3.86%newTimeline
MBCMASTERBRAND INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 650,000 shares; 2024Q4: 1,475,000 shares; 2025Q1: 1,302,500 shares; 2025Q2: not reported; 2025Q3: 2,300,000 shares 2,300,000$30.3M3.79%newTimeline
CTRICENTURI HOLDINGS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 1,300,000 shares; 2025Q1: 1,220,591 shares; 2025Q2: 2,032,000 shares; 2025Q3: 1,375,000 shares 1,375,000$29.1M3.64%-657,000Timeline
CLFDCLEARFIELD INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 695,000 shares; 2024Q4: 720,000 shares; 2025Q1: 687,200 shares; 2025Q2: 625,200 shares; 2025Q3: 625,200 shares 625,200$21.5M2.69%0Timeline
EXPEAGLE MATLS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 90,000 shares 90,000$21M2.62%newTimeline
NPKINPK INTERNATIONAL INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 1,226,808 shares; 2025Q3: 1,576,808 shares 1,576,808$17.8M2.23%+350,000Timeline
CTOSCUSTOM TRUCK ONE SOURCE INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2023Q4: restricted; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 1,875,000 shares; 2025Q3: 1,925,000 shares 1,925,000$12.4M1.55%+50,000Timeline

Sold out in Q3 2025

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

SecurityShares beforeValue beforeType
DYDYCOM INDS INC224,700$54.9Mshares
MYRGMYR GROUP INC265,200$48.1Mshares
RRXREGAL REXNORD CORPORATION275,000$39.9Mshares
MRC GLOBAL INCMRC GLOBAL INC2,267,000$31.1Mshares
MIRMIRION TECHNOLOGIES INC1,337,000$28.8Mshares
MTZMASTEC INC125,000$21.3Mshares
MTRXMATRIX SVC CO1,087,100$14.7Mshares
DXPEDXP ENTERPRISES INC75,600$6.63Mshares

How Q3 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 0001510940-25-000006 base2025-11-14acceptance time not in the bulk data set