This means that you'll be able to search for NAICS codes directly (if that's your jam). We'll do the math; let's make better data on public procurement together.
Quality Control Services: Railway Equipment
Possible NAICS Codes
561210 – Facilities Support Services
482111 – Line-Haul Railroads
423850 – Service Establishment Equipment and Supplies Merchant Wholesalers
332312 – Fabricated Structural Metal Manufacturing