The "Automatic Fuel Shut-Off Valve" closes automatically when you turn your ignition key off, and opens when you turn your ignition key on. You will never have to worry about gas running into your carburetor or worse, ruining your engine. No need to manually close your sediment bowl valve every time you turn your engine off. Installs easily, is made to fit the 9N, 2N, and 8N Fords, but will probably fit others. 6 volt and 12 volt available.