"By Wolo, these air powered horns are super loud have 2 options of a two tone alternating blast or one steady blast. Works on any 12 volt system. Consists of 2 chrome metal trumpets with the longest 8 ½ inches, air compressor and all mounting hardware. Instructions in English and Spanish. 120 Decibels-512/625 Hz. Pair. Optional Weather Protection Cap sold separate, Add On part 415WPC, $14.95.