Atoplee 4-12mm TI-Coated HSS Spiral Grooved Step Drill Set,Triangle Shank Material: High-speed steel 4241; Surface treatment: titanium Shank type: Triangle Shank;Shank Diameter:6mm Step Quantity:5steps Step Diameter:(4 , 6 , 8 , 10 , 12 )mm Package Included: 1pc Titanium Spiral Groove Step Drill Bit