| Business | Phone |
| Hinkle Engineering Inc 8167 S Cass Ave, Darien 60561 | (630) 910-7425 |
| Industrial Cost Engineering 1014 Hinsbrook Ave, Darien 60561 | (630) 971-8200 |
| J & S Power Solutions 1301 Darien Club Dr, Darien 60561 | (630) 434-9388 |
| Prime Engineers Ltd 7900 S Cass Ave 120, Darien 60561 | (630) 852-4405 |
| Transtruct Engineering Support 2131 Green Valley Rd, Darien 60561 | (630) 910-4900 |