Single ball raceway swivel caster with 1/2in. diameter king pin. Zinc-plated, 12-gauge steel fork and top plate. 3in. polyolefin wheel, 1 1/4in. tread width. 3 3/4in. overall height. 3 3/16in. x 4 1/8in. top plate with bolt hole spacing of 22 3/64in. x 31 1/32in.. 250-lb. load capacity per caster.