You'll know it when you hear it! It comes with everything you need to get your horn working: an extremely reliable compressor, 1.5-gallon air tank, and a pre-wired pressure switch. All you have to do is hook up two wires and this air system comes to life! Coupled with the two-wire horn installation above, this kit is extremely simple to install!Unlike some other train horn kits in this price range, our kit comes with lots of little extras that shouldn't be underestimated. Paired with this durable, beautiful horn is a complete HornBlasters onboard air source. This system features a drain cock, 145 PSI safety blow-off valve, a pre-wired pressure switch, and most importantly a one year warranty.