The FLI-Light is used to monitor the amount of fuel remaining in your fuel tank. The system uses non-contact sensors that are designed to work on non-metallic fuel tanks without any drilling, cutting or contact with the fuel. The remaining fuel is broken up into 4 levels. When the remote button is pressed the remaining fuel level is read and displayed via the built-in L.E.D. indicator. These will not work on Metallic gas tanks.