Wolo (837 Cannon Ball Express Truck Horn - 12 Volt Electric Solenoid Operated Will give any 12-volt truck the powerful sound of a train air horn Perfect choice when a truck owner demands an ultra-powerful horn Constructed of all metal with three triple chrome plated trumpets Requires an on-board air system Horn comes with all required mounting hardware, 10 foot length of 1/4 inch nylon high pressure hose and a heavy-duty 12-volt electric solenoid valve