Rated for loads up to 420 pounds, this rigid plate caster is made of zinc. The mounting plate is 4 1/8 x 3 3/8 inches, with inside and outside bolt hole spacing of 2 3/8 x 3 1/8 inches, with a 5/16-inch mounting bolt diameter. The grey, poly-loc wheel is 1 1/2 inches wide and four inches in diameter. The replacement wheel number is WPP4BG.