Product Name : Hexagonal Shaft Short Drill Blade Edge: Tri-Blade Material: Cobalt High Speed Steel (HSS-Co/M35) Surface Treatment: TiAlN Titanium Coating Hardness: HRC89 Size: 3.0, 3.2, 4.0, 4.2, 4.5, 5.0, 6.0, 6.5 mm Set Includes: 8 pcsShank diameter: 1/4 inch hex shank (0.25 inch (6.35 mm)); Storage: Blister 1 Uses: For drilling holes in stainless steel, iron, copper, aluminum, wood, resin, etc.