Aquatec Scuba-Alert Horn for BC/BCD Inflators This great Sub-Alert features: Signal both underwater and on the Surface Volume: Approx. 115-125 dB. It's very loud so be sure to keep it away from your ears Easy clean and rinse with fresh water after use Easy to activate red Horn Button Very compact in size The best quality components Creates loud resonating frequency Can be heard on the surface for approximately 1 Kilometer Major requirement for many live-aboards and dive operations Comes in two models: AH-150-01: The Standard Power Inflator AH-150-03: SeaQuest AirSource, Apeks Octo Plus, Beauchat Venturi, Aqua Lung Air Mic, Oceanic Air XS, and the Zeagle OctoPlus Essential piece of gear that will add to the enjoyment of your dive. Dive smart and afford to dive!