Listing is for a set of four (4) Service Caster Series #20 1-1/2" expanding stem 316 stainless steel swivel casters, two (2) with top locking brakes, with 3-1/2" diameter by 1-1/4" wide gray polyurethane wheels capable of supporting a total weight of 1,000 lbs. (250 lbs./caster). When searching for a reliable and durable solution to your caster needs, consider Service Caster?s 316 stainless steel polyurethane wheel casters. SS316 casters are ideal for light and medium duty material handling, carts, equipment, and shop projects. Built with 316 stainless steel, which contains additional molybdenum and nickel content, making it more corrosion resistant than standard 304 stainless steel. The non-marking, non-marring polyurethane wheels perform especially well on hard surfaces such as concrete, tile, and wood. Mounting options include top plate, bolt hole, expanding stem and standard and metric threaded stem sizes. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Count on us to move you forward.