This Loud Train Sound Air Horn is entirely made of 4 trumpets metal . Comes with a 1 gallon (3 liter) air tank, 150 PSI 12 volt Air compressor, air pressure gauge, air pressure switch, high pressure air hose, mounting hardware, electric air valve solenoid, Teflon tape sealer, installation instructions, and a FREE horn button. Horn system will produce a loud train sound at 149 decibels, and surely will get anybody's attention around you. Great for Cars, SUV, Trucks, RV's and Boats and many other applications. Trumpet sizes: 16-3/4", 14-3/4", 11-3/4", 9-1/4". Air Tank/Compressor dimensions: 17-3/4" L x 8-1/2" H x 8-1/2" W