The Acou-Stick Underwater Noise Maker is patented technology used by divers, Dive Masters, and Scuba instructors worldwide. Get your dive buddy's attention fast and easily--just a simple shake sends sound up to 100' (30m)! No batteries or maintenance required! Unlike simple "rattling" devices, the Acou-Stick Professional Underwater Communicator stays silent while swimming and when stowed in dive gear or luggage. It only works when you want it to! This virtually indestructible device is constructed from high impact, high strength polymer for years of maintenance-free use. Acou-Stick is compact; at only 6" (15.24cm) long, it will fit easily in to your BCD pocket, making it handy when you need it. Acou-Stick comes equipped with a 12" (30.5cm) nylon wrist strap. If you do happen to drop the Acou-Stick, the high visibility fluorescent green color will make it easy to locate. The Acou-Stick is near neutrally buoyant for ease of carrying, and it is proudly made in the USA.