The difference between these kits is the size of the air tank and the air compressor. The 2-gallon air tank provides about 3-4 seconds of honk time, while the 5-gallon air tank extends this to 8-10 seconds. The 5-gallon system also features a heavy-duty air compressor that refills the tank faster, making it better suited for airing up tires or powering air tools. Both kits are equipped with the Shocker XL train horns, producing the authentic sound of a locomotive.