Under-deck hidden horn is designed for vessels under 12 meters (39.4'), draws less than 1/2 amp and is easily installed in a standard 2-1/4 cut-out. Each unit is completely sealed. Includes a waterproof gasket while the openings are sealed with Gore-Tex® to let sound out but prevents water from coming in. Single: 2-5/8"W x 4-3/8"L x 1-3/4"D.106-108dB(A)Double: 3"W x 6-1/8"L x 1-3/4"D. 110-112dB(A)