i have the 4 horn from siege engineering under my back bumper, and i have a 5 gallon with 2 compressors for it, i was running my cylinders off of it too but i took them off for the winter. Im going to be putting it all up for sale very soon and i have no use for the horn when i have no tank so watch classifieds, i think ill put it up later today once i take pictures of everything. My buddy bought one of the entire kits, comes with a 3 liter tank and compressor (the compressor burnt up within 30 minutes of use). Its overpoweringly loud, but with a small tank like that you can only get small burps before your out of air, and quickly lose pressure... the pressure it what makes it so loud. Mine is pretty dirty since its been under my car for about 2 months and it just started snowing here, but its practically brand new and will clean up all shiny chrome again.