This new AQUATEC Duo Alert is very compact in size. Only the best quality components are used in manufacturing of the AQUATEC Duo-Alert. The loud resonating frequency generated by this horn can be heard on the surface or approximately over a 1.0K range and U/W approximately 100 meters The AQUATEC Duo-Alert is not only stating to be major requirement for many Dive-aboard and dive operations; it is also an essential piece of gear that will add to the enjoyment of the dive to any buddy team that need to get each others attention underwater. The Duo-Alert is a dual function signaling device. It is actually a Scuba-Horn and Scuba-Alert built together in one unit. It comes with 3 designs for different type BCDs; Model I (Standard) - Fits all styles of BCs except if fitted with the a breathable type inflator; Model II - Fits Sherwood Gemini, Tusa Duo-Air, DiveRite RiteSource, H2Odyssea Inflator plus, Zeagle Octo-Z, Atomic SS1 or Scuba Pro Air II; Model III - Fits Aeris Air Link, Oceanic Air XS2, Zeagle Octo+, Aqualung Air Mic, Seaquest Air Source, Apeks Octo+ or Beuchat Venturi system.