| Business | Phone |
| Abdelmalek & Assoc Inc 13610 Barrett Office Dr # 200, Ballwin 63021 | (314) 965-7000 |
| Uma Engineering Inc 13515 Barrett Parkway Dr # 260, Ballwin 63021 | (314) 835-0800 |
| Siebert Materials Engineering 1310 Parkview Valley Dr, Ballwin 63011 | (636) 227-3583 |
| Rrs Engineering 128 Enchanted Pkwy, Ballwin 63021 | (636) 230-5302 |
| Rrs Engineering 459 Pine Hollow Ct, Ballwin 63021 | (636) 230-5302 |
| N C Roden & Assoc Inc 772 Penny Ct, Ballwin 63011 | (636) 394-7510 |
| Mcenery Automotive Corp 13523 Barrett Parkway Dr, Ballwin 63021 | (314) 909-9100 |
| Marston & Marston Inc 13515 Barrett Parkway Dr # 260, Ballwin 63021 | (314) 984-8800 |
| J Jo Control Systems 221 Old Meramec Station Rd, Ballwin 63021 | (636) 230-3302 |
| C K Engineering Inc 116 Holloway Rd, Ballwin 63011 | (636) 394-3331 |