MaterialMark a starting point with pins made of metal (steel, aluminum, brass, copper), wood, glass, leather or plastic and prevent drills or screws from slipping. AdjustableThe automatic center punch has a built-in spring to adjust the tension, you can adjust the cover clockwise or counterclockwise to get it just right and hold very well Wild ApplicationAutomatic center punch can be used as manual punch tool on wood, soft metal, glass; it can also be used to break car windows for you to escape in an emergency Easy to Use: Simple one-handed operation without hammer. Anyone who only has one hand available to strike won't want to be without this tool. You will find the self-punching punches to be a good addition to the household tool kit. SpecificationMetal grit is 128mm (5.04 inch) long and 11mm (0. 49 inch) in diameter. The set contains two automatic center punches and two replacement punches. The outer shape is compact and easy to carry