HSS PRECISION STEP DRILL SET 4mm - 30mm Set of 3 HSS step drills.For cutting 4mm - 30mm diameter holes.Manufactured from quality HSS 4341 for durabilityStraight Flutes allow clog free, precision drilling of various sheet materialsEighteen different size holes between 4mm-30mm with just three bits.Drill 1 has a 6mm diameter shank and drills sizes: 4, 5, 6, 7, 8, 9, 10, 11, 12mm.Drill 2 has an 8mm diameter shank and drills sizes: 4, 6, 8, 10, 12, 14, 16, 18, 20mm.Drill 3 has a 10mm diameter shank and drills sizes: 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30mm.Supplied in a robust case.