3.5 Inch SS Red Poly Wheel Swivel 1-3/4 Inch Expanding Stem Caster. Listing is for one (1) Service Caster Series #20 1-3/4" expanding stem stainless steel swivel caster with a 3-1/2" diameter by 1-1/4" wide red polyurethane wheel capable of supporting 300 lbs./caster. When searching for a reliable and durable solution to your caster needs, look no further than the Service Caster Series 20 expanding stem red polyurethane wheel casters. The Series #20 features an innovative expanding stem that can easily adapt to the inside diameter of the opening, allowing for a secure fit in round or square tubes. Simply tighten the topmost knurled nut to compress the rubber for a snug fit.