[Step Drill Size]: 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm. A variety of drill bits can meet your different needs, saving time and money. [Premium materials]: These step drill bits are made of heat treated 4241 high speed steel (HSS) and titanium nitride coated. The titanium coating can reduce friction and operating temperature, which can effectively extend the service life. [Staggered structure]: The drill bit can drill holes of different specifications without the need to purchase multiple drill bits, saving space and money. [Double Groove]: Automatic deburring when drilling. Cutting is faster and smoother. Three flat handles ensure a firm grip. Triangular round shank: can be easily installed in electric screwdriver, drill bit and pressure drill. [Applicable]: The step drill set can be used for workpieces with hardness less than 25° and thickness less than 5mm. Suitable for various materials, such as carbon steel, iron sheet, insulation board, PVC board, wooden board and wood, etc. They also help to enlarge existing holes and are not recommended for stainless steel. Hand department：12mm Note: The data are all manual measurement, please allow 1 - 62cm, due to the difference in light and display, there will be a certain color difference, depending on the physical object received.