Guardian Fuel Alarms were designed to attach to the fuel tank of your vehicle to deter thieves from stealing gas by drilling a hole in your gas tank. Mounted to your gas tank, the alarm monitors any vibrations detected in the area and when alerted produces an ear piercing 113 decibel alarm. Waterproof, shockproof, and shielded from heat, Guardian Fuel Alarms can take a beating from the everyday conditions you find beneath vehicles. Every unit comes with directions on how and where to best install your alarm, as well as a 'Guardian Undercarriage Alarm' sticker to let thieves know its not worth messing with your vehicle.