✔Made with drop forged heat treated high speed steel (HSS) with titanium nitride coating for longer life time. ✔High speed, titanium nitride coated steel Replaces 28 separate drill bits Two fluted design for fast, smooth cutting. ✔Automatically deburrs holes as you drill. ✔4241 high-speed steel, used in hardness under 25 ° workpiece, the plate thickness under 5 mm. ✔such as carbon steel plate, sheet iron, insulation boards, wood. Cannot be used for stainless steel. ✔When inject cold water while working, can effectively extend the service life of the drill bit.