This 4" x 1-1/4" wide swivel caster has both upper and lower ball bearings in the swivel race. The wheel is a ball bearing polyurethane tread bonded to a polyolefin core. This design adds strength for loads subject to shock and hard impacts. The tread is molded in, around and through the core to prevent debonding. Resistant to most chemicals, solvents, water and acids. This is a knock off of the Colson Domestic caster, The weight rating is lower (230lbs).