Gardner Bender dies are interchangeable, in any combination, with most brands of knockouts. Constructed from black oxide coated, hardened and tempered chrome-moly steel. Use this 4 Inch Die in combination with GB 4-point slug-outs to punch clean, round holes through 10-gauge mild steel, 12-gauge stainless steel or other soft metals up to .135 inches in thickness. Additional sizes available to specifically permit fast and easy installation of electrical conduit and pipe of nominal sizes 1/2 through 4, in all commonly available increments.