4" x 2" Polyon Cast Wheel Rigid Caster - 800 lbs. Capacity4" x 2" Polyon Cast Wheel Rigid Caster Polyurethane elastomer tread chemically bonded to a cast iron core. These wheels are somewhat heavy and are ideal for warehouses with concrete and hardwood flooring. Tread: Polyurethane Elastomer Core: Cast Iron Bearing: Roller Bearing Rig: Zinc Plated Rigid Caster, 4" x 4 1 2" Mounting Plate Capacity: 800 Lbs. Color: Green and Black Durometer: Shore A 95 (+ 5) Temperature: 40 F to 180 F Load Capacity 800 Lbs.