Sure, you can find casters with threaded male studs at all of your better home improvement centers, as well as regular old-fashioned hardware stores, but they only stock casters with the larger-diameter 3/8" thread. Trust us - we've already checked! Most of your commercial-grade steel shelving units however come equipped with only 5/16" holes. It is [...]a lot easier mounting the smaller 5/16" diameter threaded casters than it is drilling out the holes in 20 guage steel to accomodate 3/8" studs! To the best of our knowledge, Specialty Store Services is the only supplier in the country which regularly stocks your smaller 5/16" threaded male stud casters.