... proper lubrication. TheHss step drills have following size:Sizes: 4-12 mm step: 4, 6, 8, 10, 12 mm 40-20 mm step: 4, 6 ... , 8, 10, 12, 14, 16, 18 ... , 19, 24.5, 28 mm 40-30 mm step: 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 ... , 30 mm 4-39 mm step: 4, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36 ...