Viking Horns V504 Electric 1/4" Iline Air Valve Solenoid for Train Horns, Suspension, and Many More Uses Construction: Metal housing Includes brass compression fittings to fit 1/4" O.D air hose Power source: Requires 12 volts Mounting Hardware: bolts, lock washers & nuts Valve Dimensions: 3-1/4" long x 4" Deep x 2-3/4" High