This medium-duty swivel caster has a four-inch phenolic wheel with a width of 1 1/2-inch supported by a zinc frame. This caster has a mounting plate measured at 4 1/8 inches long and 3 3/8 inches wide with a bolt diameter of 5/16-inch. The inside and outside bolt hole spacings are 2 3/8 inches long and 3 1/8 inches wide.