... size:Sizes: 4-12 mm step: 4, 6, 8, 10, 12 mm 40-20 mm step: 4, 6, 8 ... , 10, 12, 14, 16, 18, 20 mm 5-28 mm ... .5, 28 mm 40-30 mm step: 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 ... , copper, aluminum, wood and plastic. Drills up to 1/2" holes sizes with one bit. Ideal tool for sheet metal ... shank prevents slipping in drill chuck or bit extension. high precision Hss 2 step drills