6" x 2" Polyon Cast Swivel Caster w/ Total Lock Brake - 1200 lbs. Cap.6" x 2" Polyon Cast Wheel Swivel Caster with Total Lock Brake 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 Swivel Caster, 4" x 4 1 2" Mounting Plate, Total Lock Brake Capacity: 1,200 Lbs. Color: Green and Black Durometer: Shore A 95 (+ 5)