| HHubbard | Hubbard | OH | 20–99 | ◐ LIKELY ACTIVE |
| HGHubbell Gas Utility Solutions | Broken Arrow | OK | 100–499 | ◐ LIKELY ACTIVE |
| HCHub City Sprinklers, INC. | Hagerstown | MD | — | ◐ LIKELY ACTIVE |
| HEHunting Energy Services Subsea Technologies Division | Stafford | TX | 100–499 | ◐ LIKELY ACTIVE |
| HEHunting Energy Services Subsea Technology Division | Spring | TX | 20–99 | ◐ LIKELY ACTIVE |
| HSHuntington Steel & Supply CO | Huntington | WV | — | ◐ LIKELY ACTIVE |
| HAHurricane Architectural Metals, Inc. | Naples | FL | 1–19 | ◐ LIKELY ACTIVE |
| HFHurtt Fabricating Corp (North Plant) | Marceline | MO | 1–19 | ◐ LIKELY ACTIVE |
| HAHVAC and Plumbing Fab Shop | Baltimore | MD | 20–99 | ◐ LIKELY ACTIVE |
| HWH. W. Metal Products, Inc. | Tualatin | OR | 20–99 | ◐ LIKELY ACTIVE |
| HSHybrid Steel Design LLC | Fort Benton | MT | — | ◐ LIKELY ACTIVE |
| HTHydro Tube Enterprises, Inc | Oberlin | OH | 20–99 | ◐ LIKELY ACTIVE |
Hygrade Metal Moulding Manufacturing Corp - Arkansas | Magnolia | AR | 20–99 | ◐ LIKELY ACTIVE |
Hygrade Metal Moulding Manufacturing Corp - Oregon | Milwaukie | OR | 1–19 | ◐ LIKELY ACTIVE |
Hygrade Metal Moulding Manufacturing Corp - Pennsylvania | Bethlehem | PA | 20–99 | ◐ LIKELY ACTIVE |
Hygrade Metal Moulding Manufacturing Corp - Tennessee | Mount Pleasant | TN | 20–99 | ◐ LIKELY ACTIVE |
| HIHynes Industries, Inc. - Youngstown, OH | Youngstown | OH | 100–499 | ◐ LIKELY ACTIVE |
| HIHynes Industries- Kokomo | Kokomo | IN | 20–99 | ◐ LIKELY ACTIVE |
| HIHynes Industries- Painesville | Painesville | OH | 20–99 | ◐ LIKELY ACTIVE |
| HIHynes Industries- Youngstown | Youngstown | OH | 100–499 | ◐ LIKELY ACTIVE |
| HIHyprio INC. | Mount Pleasant | SC | — | ◐ LIKELY ACTIVE |
| HFHysa Fillers L.l.c. | Golden | CO | — | ◐ LIKELY ACTIVE |
| HPHyspan Precision Products, INC. | Alpharetta | GA | — | ◐ LIKELY ACTIVE |
| IIIce Industries Bowling Green | Bowling Green | OH | 20–99 | ◐ LIKELY ACTIVE |
| IIfab | Gastonia | NC | 100–499 | ◐ LIKELY ACTIVE |
| IIIfi International Fabrication Industries LLC | Lapeer | MI | — | ◐ LIKELY ACTIVE |
| ILIMIA, LLC Charleston | Goose Creek | SC | 1–19 | ◐ LIKELY ACTIVE |
| ILIMIA, LLC Rosemont Structural | Chesapeake | VA | 20–99 | ◐ LIKELY ACTIVE |
| IFImpact Fab | Holland | MI | 20–99 | ◐ LIKELY ACTIVE |
| IMImperial Manufacturing Group | Alton | IL | 100–499 | ◐ LIKELY ACTIVE |
| ICIndian Creek Fabricators INC. | Tipp City | OH | — | ◐ LIKELY ACTIVE |
| ISIndustial Steel Constructors | Denham Springs | LA | 1–19 | ◐ LIKELY ACTIVE |
| IMIndustrial Metal Enterprises LLC | Blackfoot | ID | 20–99 | ◐ LIKELY ACTIVE |
| IMIndustrial Metal Works LLC | Newtown | CT | — | ◐ LIKELY ACTIVE |
| IPIndustrial Products Group, LLC | Chesapeake | OH | — | ◐ LIKELY ACTIVE |
| IRIndustrial Resources, Inc. | Fairmont | WV | 20–99 | ◐ LIKELY ACTIVE |
| IRIndustrial Rigging Services of Central Texas | Hewitt | TX | 20–99 | ◐ LIKELY ACTIVE |
| ISIndustrial Steel South LLC | Rockledge | FL | 1–19 | ◐ LIKELY ACTIVE |
| IFInfrastructure Fabrication LLC | Bath | PA | — | ◐ LIKELY ACTIVE |
| IMInterior Mobile Welding & Services INC | Fairbanks | AK | — | ◐ LIKELY ACTIVE |
| ICInvicta Contracting LLC | Osburn | ID | — | ◐ LIKELY ACTIVE |
| IGIra G Steffy & Son, Inc. | Ephrata | PA | 100–499 | ◐ LIKELY ACTIVE |
| ISIron Sharpens Iron Welding & Fabricating, INC | Minneola | FL | — | ◐ LIKELY ACTIVE |
| ISIrwin Steel LLC | Justin | TX | 100–499 | ◐ LIKELY ACTIVE |
| IDIsidore DBA Twin Oaks Manufacturing | San Jose | CA | 1–19 | ◐ LIKELY ACTIVE |
| ILIstanbul Logistics Aluminum Trading LLC | Vienna | VA | — | ◐ LIKELY ACTIVE |
| IBITW Building Components Group Inc - Earth City, MO | Earth City | MO | 1–19 | ◐ LIKELY ACTIVE |
| IBITW Building Components Group Inc - Ft. Lauderdale | Fort Lauderdale | FL | 20–99 | ◐ LIKELY ACTIVE |
| IBITW Building Components Group Inc - Glenview, IL | Glenview | IL | 500+ | ◐ LIKELY ACTIVE |
| IBITW Building Components Group Inc - Grand Prairie, TX | Grand Prairie | TX | 20–99 | ◐ LIKELY ACTIVE |