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ACK Asset Management LLC

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13F filer, CIK 1510940, GREENWICH, CT

ACK Asset Management LLC reported $856,327,037 across 21 holdings for the quarter ended 2026-06-30, in a 13F-HR filed 2026-08-13. Its ten largest share positions make up 60.24% of the portfolio.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001510940-26-000005

Period
2026-06-30
Reported value
$856M
Holdings
21
Top 10 weight
60.24%
New
7
Sold out
6

Largest buys vs the previous quarter

SecurityShares changeApprox. value
GTXnew+1,500,000$54.3M
BWAnew+600,000$39.8M
DNOWnew+3,000,000$38.9M
STnew+600,000$28.6M
SHLSnew+2,255,000$22.3M

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
MTRNreduced-339,800-$101M
ROGexited-475,000-$51M
NOVTexited-375,000-$44.3M
DXPEexited-260,000-$36.3M
CDNLexited-874,000-$34.7M

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 2026

Share positions as resolved from 13F-HR 0001510940-26-000005, largest first. % of portfolio is the value over $856,327,037, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
WMSADVANCED DRAIN SYS INC DELQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 345,000 shares; 2025Q3: 390,000 shares; 2025Q4: 390,000 shares; 2026Q1: 390,000 shares; 2026Q2: 390,000 shares 390,000$61.2M7.15%0Timeline
HLIOHELIOS TECHNOLOGIES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 770,000 shares; 2025Q4: 780,378 shares; 2026Q1: 780,378 shares; 2026Q2: 681,000 shares 681,000$60.8M7.1%-99,378Timeline
LFUSLITTELFUSE INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: 135,000 shares; 2026Q2: 125,000 shares 125,000$56.9M6.65%-10,000Timeline
JHXJAMES HARDIE INDS PLCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 2,100,000 shares; 2025Q4: 2,100,000 shares; 2026Q1: 2,100,000 shares; 2026Q2: 2,100,000 shares 2,100,000$55M6.42%0Timeline
GTXGARRETT MOTION INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 1,500,000 shares 1,500,000$54.3M6.35%newTimeline
CNMCORE & MAIN INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 900,000 shares; 2025Q4: 900,000 shares; 2026Q1: 900,000 shares; 2026Q2: 1,090,000 shares 1,090,000$52.6M6.14%+190,000Timeline
EXPEAGLE MATLS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 90,000 shares; 2025Q4: 165,000 shares; 2026Q1: 165,000 shares; 2026Q2: 220,000 shares 220,000$49.5M5.78%+55,000Timeline
ATSATS CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 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; 2025Q4: 1,846,196 shares; 2026Q1: 1,846,196 shares; 2026Q2: 1,500,000 shares 1,500,000$43.2M5.04%-346,196Timeline
ASTEASTEC INDS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 701,500 shares; 2025Q4: 786,500 shares; 2026Q1: 786,500 shares; 2026Q2: 690,276 shares 690,276$42.2M4.93%-96,224Timeline
MTRNMATERION CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: 505,500 shares; 2024Q4: 494,800 shares; 2025Q1: 459,200 shares; 2025Q2: 524,800 shares; 2025Q3: 524,800 shares; 2025Q4: 474,800 shares; 2026Q1: 474,800 shares; 2026Q2: 135,000 shares 135,000$40.1M4.69%-339,800Timeline
BWABORGWARNER INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: 351,400 shares; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 600,000 shares 600,000$39.8M4.65%newTimeline
DNOWDNOW INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 3,000,000 shares 3,000,000$38.9M4.54%newTimeline
MBCMASTERBRAND INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: 650,000 shares; 2024Q4: 1,475,000 shares; 2025Q1: 1,302,500 shares; 2025Q2: not reported; 2025Q3: 2,300,000 shares; 2025Q4: 2,300,000 shares; 2026Q1: 3,700,000 shares; 2026Q2: 3,700,000 shares 3,700,000$38.1M4.45%0Timeline
SITESITEONE LANDSCAPE SUPPLY INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: 100,000 shares; 2025Q2: 250,000 shares; 2025Q3: 280,000 shares; 2025Q4: 330,000 shares; 2026Q1: 330,000 shares; 2026Q2: 330,000 shares 330,000$37.8M4.41%0Timeline
SWIMLATHAM GROUP INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: 5,160,000 shares; 2026Q2: 5,660,000 shares 5,660,000$36.6M4.28%+500,000Timeline
CLFDCLEARFIELD INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: 695,000 shares; 2024Q4: 720,000 shares; 2025Q1: 687,200 shares; 2025Q2: 625,200 shares; 2025Q3: 625,200 shares; 2025Q4: 625,200 shares; 2026Q1: 735,200 shares; 2026Q2: 810,200 shares 810,200$32.2M3.76%+75,000Timeline
STSENSATA TECHNOLOGIES HLDG PLQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 600,000 shares 600,000$28.6M3.34%newTimeline
AERO-SWXAERO-SWXQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: 154,851 shares; 2026Q1: 830,000 shares; 2026Q2: 1,082,500 shares 1,082,500$28.5M3.32%+252,500
SHLSSHOALS TECHNOLOGIES GROUP INQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 2,255,000 shares 2,255,000$22.3M2.61%newTimeline
EQPTEQUIPMENTSHARE COM INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 1,064,830 shares 1,064,830$20.9M2.44%newTimeline
MEIMETHODE ELECTRS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: not reported; 2026Q2: 877,500 shares 877,500$16.6M1.94%newTimeline

Sold out in Q2 2026

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

SecurityShares beforeValue beforeType
ROGROGERS CORP475,000$51Mshares
NOVTNOVANTA INC375,000$44.3Mshares
DXPEDXP ENTERPRISES INC260,000$36.3Mshares
CDNLCARDINAL INFRASTRUCTURE GROU874,000$34.7Mshares
GVAGRANITE CONSTR INC250,000$30Mshares
CTSCTS CORP584,000$27.9Mshares

How Q2 2026 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 0001510940-26-000005 base2026-08-13acceptance time not in the bulk data set

Filings

Every filing of this filer: 13F reports and notices, the 13D and 13G it filed or is a reporting person of, and Forms 3, 4 and 5 it reported as an owner.

FilingSubjectFiledAcceptedIngested
13F-HR 0001510940-26-000005 Quarter ended 2026-06-302026-08-13acceptance time not in the bulk data set
13F-HR 0001510940-26-000004 Quarter ended 2026-03-312026-05-15acceptance time not in the bulk data set
13F-HR 0001510940-26-000001 Quarter ended 2025-12-312026-02-13acceptance time not in the bulk data set
13F-HR 0001510940-25-000006 Quarter ended 2025-09-302025-11-14acceptance time not in the bulk data set
13F-HR 0001510940-25-000005 Quarter ended 2025-06-302025-08-13acceptance time not in the bulk data set
13F-HR 0001510940-25-000002 Quarter ended 2025-03-312025-05-13acceptance time not in the bulk data set
13F-HR 0000899140-25-000241 Quarter ended 2024-12-312025-02-13acceptance time not in the bulk data set
13F-HR 0000899140-24-001197 Quarter ended 2024-09-302024-11-13acceptance time not in the bulk data set
13F-HR 0000899140-24-000847 Quarter ended 2024-06-302024-08-13acceptance time not in the bulk data set
13F-HR 0000899140-24-000588 Quarter ended 2024-03-312024-05-14acceptance time not in the bulk data set
13F-HR 0000899140-24-000209 Quarter ended 2023-12-312024-02-13acceptance time not in the bulk data set
13F-HR 0000899140-23-001054 Quarter ended 2023-09-302023-11-13acceptance time not in the bulk data set
13F-HR/A 0000899140-23-000897 Quarter ended 2023-06-302023-08-15acceptance time not in the bulk data set
13F-HR 0000899140-23-000885 Quarter ended 2023-06-302023-08-14acceptance time not in the bulk data set
13F-HR 0000899140-23-000621 Quarter ended 2023-03-312023-05-12acceptance time not in the bulk data set
13F-HR 0000899140-23-000348 Quarter ended 2022-12-312023-02-14acceptance time not in the bulk data set
13F-HR 0001567619-22-019727 Quarter ended 2022-09-302022-11-14acceptance time not in the bulk data set
13F-HR 0001567619-22-016070 Quarter ended 2022-06-302022-08-15acceptance time not in the bulk data set
13F-HR 0001567619-22-010420 Quarter ended 2022-03-312022-05-13acceptance time not in the bulk data set
13F-HR 0001567619-22-003982 Quarter ended 2021-12-312022-02-14acceptance time not in the bulk data set
13F-HR 0001567619-21-019929 Quarter ended 2021-09-302021-11-12acceptance time not in the bulk data set
13F-HR 0001567619-21-013274 Quarter ended 2021-06-302021-07-13acceptance time not in the bulk data set
13F-HR 0001567619-21-010008 Quarter ended 2021-03-312021-05-14acceptance time not in the bulk data set
13F-HR 0001567619-21-003398 Quarter ended 2020-12-312021-02-12acceptance time not in the bulk data set
13F-HR 0001567619-20-019444 Quarter ended 2020-09-302020-11-13acceptance time not in the bulk data set
13F-HR 0001567619-20-015076 Quarter ended 2020-06-302020-08-13acceptance time not in the bulk data set
13F-HR 0001567619-20-010065 Quarter ended 2020-03-312020-05-14acceptance time not in the bulk data set
13F-HR 0001567619-20-002973 Quarter ended 2019-12-312020-02-12acceptance time not in the bulk data set
13F-HR 0001567619-19-021103 Quarter ended 2019-09-302019-11-13acceptance time not in the bulk data set
13F-HR/A 0001567619-19-021142 Quarter ended 2019-09-302019-11-13acceptance time not in the bulk data set
13F-HR 0001567619-19-016770 Quarter ended 2019-06-302019-08-14acceptance time not in the bulk data set
13F-HR 0001567619-19-010567 Quarter ended 2019-03-312019-05-13acceptance time not in the bulk data set
13F-HR 0001567619-19-003174 Quarter ended 2018-12-312019-02-12acceptance time not in the bulk data set
13F-HR 0001567619-18-005537 Quarter ended 2018-09-302018-11-09acceptance time not in the bulk data set
13F-HR 0001567619-18-000486 Quarter ended 2018-06-302018-08-13acceptance time not in the bulk data set
13F-HR 0001140361-18-023262 Quarter ended 2018-03-312018-05-14acceptance time not in the bulk data set
13F-HR 0001140361-18-006539 Quarter ended 2017-12-312018-02-12acceptance time not in the bulk data set
13F-HR 0001140361-17-041985 Quarter ended 2017-09-302017-11-13acceptance time not in the bulk data set
13F-HR 0001140361-17-031749 Quarter ended 2017-06-302017-08-14acceptance time not in the bulk data set
13F-HR 0001140361-17-019934 Quarter ended 2017-03-312017-05-12acceptance time not in the bulk data set
13F-HR 0001140361-17-006033 Quarter ended 2016-12-312017-02-13acceptance time not in the bulk data set
13F-HR 0001140361-16-085864 Quarter ended 2016-09-302016-11-10acceptance time not in the bulk data set
13F-HR 0001140361-16-076480 Quarter ended 2016-06-302016-08-15acceptance time not in the bulk data set
13F-HR 0001140361-16-065248 Quarter ended 2016-03-312016-05-16acceptance time not in the bulk data set
13F-HR 0001140361-16-051742 Quarter ended 2015-12-312016-02-11acceptance time not in the bulk data set
13F-HR 0001140361-15-041262 Quarter ended 2015-09-302015-11-16acceptance time not in the bulk data set
13F-HR 0001140361-15-030978 Quarter ended 2015-06-302015-08-11acceptance time not in the bulk data set
13F-HR 0001140361-15-019728 Quarter ended 2015-03-312015-05-14acceptance time not in the bulk data set
13F-HR 0001140361-15-005979 Quarter ended 2014-12-312015-02-12acceptance time not in the bulk data set
13F-HR 0001140361-14-042040 Quarter ended 2014-09-302014-11-14acceptance time not in the bulk data set
13F-HR 0001140361-14-030594 Quarter ended 2014-06-302014-08-04acceptance time not in the bulk data set
13F-HR 0001140361-14-019730 Quarter ended 2014-03-312014-05-09acceptance time not in the bulk data set
13F-HR 0001140361-14-005734 Quarter ended 2013-12-312014-02-11acceptance time not in the bulk data set
13F-HR 0001140361-13-042069 Quarter ended 2013-09-302013-11-13acceptance time not in the bulk data set
13F-HR 0001140361-13-031961 Quarter ended 2013-06-302013-08-13acceptance time not in the bulk data set