Viking Horns V616C COMPACT 12 Volt Mini AIR COMPRESSOR For Air Horn Construction: Polished Metal Housing Air Output: 14 PSI universal fit that can be used "ONLY" for "SMALL" 1 and 2 trumpets air horns that do no require an On-Board air system Power: 12 Volt, with Positive (+), and Negative (-) Electric Terminals Size: 4- inc Height x 2- inch Diameter