This rigid plate caster is made of steel with a zinc finish, and load-rated up to 400 pounds. The mounting plate is 4 1/8 x 3 3/8 inches, with a mounting bolt diameter of 5/16 inches, and inside and outside bolt hole spacing of 2 3/8 x 3 1/8 inches. The hard rubber wheel is 1 1/2 inches wide and four inches in diameter. The replacement wheel number is WRT415B.