DRILL SIZE1(4-12mm), 1(4-20mm), 1(4-32mm) step drill. The step drills have three sizes to meet your different needs. And the package included a nylon bag. DOUBLE CUTTING BLADES: Double cutting blades and X-type opening design ensure faster and smoother cutting; 3-sided shank design can prevent the drill chuck from slipping; With the smallest pressure, the sets can cut through wood, sheet metal, steel and other surfaces. HEXAGONAL SHANKThe 1/4" (6.35mm) hex shank ) works with most drills or drills with 1/4" chuck, securely fits power tool chuck and eliminates slippage. HSS & TITANIUM COATEDMade of super tough HSS steel and titanium coated, the titanium coating ensures easy cutting of steel, sheet aluminum, brass, copper, plastic, wood, etc. APPLICATIONSuitable for sheet metal, sink, car repair, etc. Widely used to punch holes in a variety of materials like plate, aluminum, insulation board, PVC board, wood thickness within 5mm.