This Electric Solenoid (air valve) can is used with air horns that require an on-board air system for 12 volt vehicles . When the vehicle's horn button is depressed, the Solenoid becomes electrically energized, opening its chamber and permitting air pressure to reach the horn. The solenoid remains open and engaged as long as the horn button is pressed. Max rating 225 PSI. 1/2" pipe thread inlet and outlet ports. Made of solid brass. Ideal for train air horn and air suspension kits.