The battery disconnect bolts right onto the negative terminal of your battery for superior theft protection. Just loosen the black knob and your car wont start, and cannot be hot wired! Take the knob with you for the ultimate in protection. Exclusive fuse-link feature maintains just enough power so your clock setting and the preset stations on your radio wont be lost. If someone tries to start the car with the knob loose the fuse will break and the car will not start. Suitable for 6, 12 or 24 volt batteries.