Ongaro Marine Horns. Ongaro horns are now available in all stainless steel models. These durable sealed sound units are constructed of 304 stainless steel inside and out and come with a 5-year warranty. Standard models are made with stainless steel outside and diaphragm only. All Ongaro horns meet ABYC specification A-23 for boats up to 12 meters (39'). Pre-wired and designed to fit existing hole patterns. Mini Compact Dual - Max. amp draw: 6 amps • 111 dB rating • 3"L x 8"W x 1-3/4"H.