Atoplee 1pc 10-45mm Spiral Groove Drilling Ladder Step Drill Bit, Nitriding HSS Made with high quality steel 4241 for longer life. Works on plastic, wood and most metals, including steel, brass, aluminum and copper Saves time without changing drill bits. Two flute design for smoother cutting. Step Sizes: 10 mm,15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45mm. Saves time without changing drill bits.