Simply tighten the topmost knurled nut to compress the rubber for a snug fit. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Listing is for one 1 Service Caster Series #20 1-1/2'' expanding stem stainless steel swivel caster with a 3-1/2'' diameter by 1-1/4'' wide black polyurethane wheel and a total locking brake capable of supporting 300 lbs.5'' SS Black Poly Swivel 1-1/2'' Expanding Stem Caster Total Lock Brake When searching for a reliable and durable solution to your caster needs, look no further than the Service Caster Series 20 expanding stem black polyurethane wheel casters.