Shepherd Hardware 9795 8-Inch Pneumatic Caster Wheel, Rigid Plate, Steel Hub with Ball Bearings, 5/8-Inch Bore Centered Axle 4-1/2-inch diameter centered steel hub with ball bearings and 5/8-inch bore 4-inch wide X 8-inch diameter pneumatic tire with ribbed tread 220-lb load capacity and 4-inch x 4-1/2-inch rigid plate Air filled pneumatic wheel provides cushioned ride, great for use indoors and outdoors on smooth or rough surfaces Designed for manual applications at low speeds, pneumatic casters provide a cushioned ride, shock absorption, and quiet operation