Features: High speed, titanium nit-ride coated steel Replaces 28 separate drill bits Two fluted design for fast, smooth cutting. When inject cold water while working, can effectively extend the service life of the drill bit. Recommend drilling rate of 250-250 RPM. 1mm thickness can be operated by hand drill, 2~3mm please use bench drill. The drill must continue to cool down when it is working, and it is not easy to burn. According to the need to process different diameter holes, you can achieve one-time processing of large holes, no need to replace the drill bit and positioning hole. Not suitable for hard and brittle materials such as stainless steel, glass, tile floors, walls etc. Specifications: Material: high speed steel Finish: Titanium Five Steps: 4mm, 6mm, 8mm, 10mm, 12mm Size: as picture Color: as picture Package include: 1 x High Speed Steel Step Drill Bit