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