This train horn kit features the compact HornBlasters 127H 120 PSI High Flow Air Source Kit. The air source kit takes up about a half a cubic foot of space and matched with our HornBlasters Shocker horns, you are getting one of the most compact horn systems on the market. Just because you are getting a compact horn system doesn't mean you have to sacrifice sound or product quality. The HornBlasters Shocker horns are made with a fiberglass reinforced ABS plastic and all stainless steel internals to conquer anything that you may throw at these horns. The HornBlasters 127H Air Source Kit is made with the highest quality materials and gives you an astounding 1.5 gallons of air at 120 PSI.