Atoplee HSS6542 Spiral Groove Step Drill Bit, 3pcs, for Stainless Steel Cutting Material:HSS6542 Shank Type:Triangle shank; Type:Spiral groove Shank diameter: 10mm(0.39'') for 4-32; 8mm(0.31'') for 4-20; 6mm(1/4'') for 4-12 Hole Cutter step included: 4-12/20/32mm Package Included: 1pcs HSS6542 Spiral groove STEP DRILL