High hardness, rustproof, solid and durable. Do not need additional center drilling or center punching. Fast replacement composite cone, uses drill edged principle. Drilling , one-step processing, greatly save processing steps and time costs, improve working efficiency. center punch delivering an automatic spring-driven strike when pressed against surface, it can be adjusted regulates striking force. Suitable for drilling, tapping, cutting on metal, aluminum plate, iron, etc. Features - Color: Silver. - Material: Steel. - Size: 30.00X0.30X0.30cm/11.79X0.12X0.12in - Say bye to all those chips and particles, with the design the drill bit can quickly clears them out, and leaves a clean, smooth hole. - Back tapered beyond tap to prevent thread damage from over-drilling. - Maximize efficiency with the included adapter that allows you to between different sizes easily. - The product designed with fast replacement composite cone, uses drill edged principle. - Drilling , one-step processing, greatly save processing steps and time costs, improve working efficiency. Package list: 1 x drill bit (3 x 300mm) 1 x drill bit (3.5 x 300mm) 1 x drill bit (4 x 300mm) 1 x drill bit (4.5 x 300mm) 1 x drill bit (5 x 300mm)