Denew Automatic center punch 2-piece set (128mm+155mm), spring loaded center hole punch, adjustable tension Easy one handed operation without the need for a hammer. Mark the starting point of dents on the surface of metal (steel, aluminum, brass, copper), wood, glass, leather, or plastic to prevent the drill bit or screw from slipping. Has excellent durability. Composed of chrome plated tips and high-quality stainless steel body, with anti slip knurled texture, providing you with very comfortable and precise operation. By using tensioning screws, you can adjust the optimal tension during work by simply rotating the knob. This will enable you to control the impact pressure of the dual spring loaded barrel and provide the correct indentation on the material you are using. It is not only a center punch, but also a safety tool on the car. This product can work on glass, which means that in case of any emergency, it can easily break the car window and help you escape. In addition, size is very space saving in cars.