Even tougher than high speed steel bits - last 30 times longer than standard drill bits! Bores stainless, silicon-chrome, chrome-nickel - even armor and plate Includes metal case; U.S.A. Includes (qty.): 21, Bores: Stainless, silicon-chrome, chrome-nickel, armor and plate, Case Included: Yes, Size: 1/16in. - 1/2in. by 64ths, Finish Type: Cobalt