Listing is for a set of four (4) Service Caster Series #30 stainless steel casters, two (2) swivel casters with bolt on swivel locks and two (2) rigid casters, with 8" diameter by 2" wide polyurethane tread set on a polyolefin core wheel and maintenance free precision ball wheel bearings capable of supporting a total weight of 4,000 lbs. (1,000 lbs./caster).