Made with drop forged heat treated high speed steel (HSS) with titanium nitride coating for longer life time. Secured in aluminum carrying case. High speed, titanium nitride coated steel Replaces 28 separate drill bits Two fluted design for fast, smooth cutting. Automatically deburrs holes as you drill. Six step bit: 3/16", 1/4", 5/16", 3/8", 7/16", 1/2"; Nine step bit: 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4"; Thirteen step bit: 1/8", 5/32", 3/16", 7/32", 1/4", 9/32", 5/16", 11/32", 3/8", 13/32", 7/32", 1/4", 9/32", 5/16", 11/32", 3/8", 13/32", 7/16", 15/32", 1/2"