Material: The spring-loaded punch housing is made of carbon steel and the inner spring is made of stainless steel, which is waterproof and rust-proof, high strength and durable. Adjustable Tension Design: With the powerful automatic grain, you can set the best tension for your work by simply turning the knob. This allows you to control the shock pressure on the double sprung axles and ensures the correct on the material used. What's included in the package: The package includes 4 automatic grains to more possibilities for your work. EASY OPERATION: Spring-loaded center punch for easy one-handed operation without a hammer. If you only have one hand to hit, you 't to do without this tool anymore. You'll find self-tapping punches to be a great addition to your DIY tool kit. [WIDELY USED] The automatic hole punch can be used as a manual punching tool for wood, metal and glass; besides, it can be used to smash car windows for your escape in case of emergency. Just put it on the corner of a car window and it will crack and fall and escape. Material:carbon steel Size: 12.8 x 1.2cm Package Contents: 4 x Center pitch