"The Fairbanks Rigid Weldless Caster features one-piece construction to eliminate stress build-up. Double ball raceways and seal ring keep lubrication in and dirt out. 2 5/8in. to 3in. x 3in. to 3 5/8in. bolt hole spacing. 3/4in. king pin. Top plate size 4in. x 4 1/2in. Wheel Width in. 2, Wheel Type Polyurethane/polypropylene core, Capacity lbs. 750, Casters qty. 1, Caster Type Rigid, Wheel Diameter in. 6. Zinc-Plated Forks with Polyurethane Tread/PolyEthylene Core Wheels"