1[118 X TYPE OPENING] The step drill is designed with 118 X type opening, with accurate positioning and reducing drill bit slippage. 2[DOUBLE SPIRAL FLUTES] Double spiral flutes, greatly reduces drilling resistance, with fast cutting and smoother chip removal. 3[WITH HEX SHANK] With standard hex shank, which is stable in installation, not easy to slip or fall off during use. 4[HIGH SPEED STEEL] Made of high speed steel material, with high hardness and wear resistance, not easy to deform or corrode. 5[DRILLING THICKNESS] The drilling diameter is 420mm, which can be used for 2mm thin iron, 2mm copper or aluminum plate, 4.5mm wood or plastic, etc. Item Type: Step Drill BitMaterial: High Speed SteelDrilling Diameter: Approx. 4-20mm / 0.2-0.8inDrilling Thickness: 2mm thin iron (within 25 degrees of hardness)2mm copper or aluminum plate4.5mm wood or plastic plate 1 x Step Drill Bit