6" x 2" Polyon Cast Wheel Swivel Caster Medium Heavy Duty 1200 lbs. cap.6" x 2" Polyon Cast Wheel Swivel 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 Swivel Caster With Large, Heat Treated Double Ball Raceways, 4 1 2" x 6 1 4" Mounting Plate Capacity: 1,200 Lbs. Color: Red and Silver Durometer: Shore A 95 (+ 5)