Sandusky WCASTERSET4 4-Caster Set for Wire Shelving, 4" Diameter, 660 lb. Capacity Set of four swivel casters for use with wire shelving unit (not included) Wheels with 4" diameter are made of rubber for use on carpets and hard surfaces Swivel mounts on casters allow a 360-degree change in direction Pedal-style brake on two casters help prevent rolling Set has 660 lb. capacity, equally distributed