Features: Selected from High Speed Steel, enhance durability and sharpness, ensures the hardness. It can reduce the friction and perform well in heat, corrosion, and rust resistance. This set includes 5 standard step drill bits, 1 automatic center punch, marking with it before drilling can prevent drill slippage. Smoother drilling and allowing for clean and professional result. Increase cutting speed with self-centering and prevents slipping in the drill chuck. Our step drill bit can process different diameter holes, and can be used on materials such as metal, iron, aluminum, brass, plastic, aluminum, wood Suitable for Home projects, professional. Specifications: Component:High Speed Steel Size:4-12mm 3-13mm 4-20mm 5-35mm 4-32mm Package Includes: 5Pcs Step Drill Bits 1Pc Automatic Center Punch note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.