Self-centering point, do not need assistant center drilling or center punching. Spiral groove, within the processing thread, cutting up to exclude, and was curled applied internally threaded through holes. High hardness, rustproof, solid and durable. The advantage is opening, tapping, chamfering. Drilling , one-step processing, greatly save processing steps and time costs, improve working efficiency. Save processing steps and time costs, improve efficiency. Features - Color: Silver. - Material: Steel. - Size: 30.00X0.30X0.30cm/11.79X0.12X0.12in - Heavy duty, lightweight and durable for easy storage and is portable for environments. - The drill bits set fits the majority of brands currently on the market. - Suitable for drilling, tapping, cutting on metal, aluminum plate, iron, etc. - Great drill bits metal, wood, plastic countersink. Suitable for home DIY, and general building, engineering use. - Please keep cool and gentle using, the working life of the drill bits can be largely prolonged by proper usage. 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)