Hss step drill bit with 14 steps and straight flute ø4-30 mm (4-6-8-10-12-14-16-18-20-22-24-26-28-30 mm). ø10 mm shank with triple flat grip (non-slip). drills and enlarges holes in sheet metal up to 4 mm thick. ideal for steel, non-ferrous metals and plastics.