This Electric Solenoid (air valve) can is used with air horns that require an on-board air system for 12 volt vehicles . When the vehicles 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 depressed. Max rating 225 PSI. 1/2" pipe thread inlet & outlet ports. made of solid brass. Ideal for many other applications.