This medium-duty rigid plate caster has a double ball raceway swivel sub-type and a load rating of 500 pounds. Each caster features a 1 1/2 x 5-inch phenolic wheel with a black core and a zinc frame and finish. The mounting plate measures 4 1/8 x 3 3/8 inches, with a 5/16-inch mounting bolt diameter and an inside/outside bolt hole spacing of 2 3/8 x 3 1/8 inches. Use item number MPU515B 5/8 for replacement wheels.