DRILL SIZE1 (4-32mm) Spiral Step Drill Bit, The sizes of metal drill bits are clearly laser engraved, making it easy to drill accurately. Pour water while the step drill is working, can effectively extend the service life. TIME SAVING: Step drill bit cover different step sizes, allows you to drill or enlarge different holes in a metal drill bit without changing drill bits constantly. The size is laser engraved into the metal, so it can be drilled accurately and will not wear out even if used for a long time. HSS & TITANIUM COATEDMade of super strong HSS steel and coated with titanium, titanium coating ensures easy cutting of steel, aluminum sheet, brass, copper, plastic, wood, etc. APPLICATIONSuitable for sheet metal, sink, auto repair, etc. Widely used for drilling holes in a variety of materials like plate, aluminum, insulation board, PVC board.