Coghlan's Emergency Survival Horn is a very loud emergency signal for outdoor camping, hiking and backpacking. It operates with the simplicity of a mouth horn and blasts out audible sound up to 120dB. The membrane can be easily replaced with any thin flexible film. "SOS" is printed on the body and includes a black break-away lanyard. To use, blow into the small hole located on the side of the horn. The blast of sound will exit through the back of the horn through the dual chamber horn. This self-powered, compact horn produces super loud blast of sound that can be heard for over one mile and frightens off unfriendly animals. The durable polypropylene construction floats in water and has a highly visible orange color. Stone and twig guard protects the rubber membrane. Eco-friendly; No compressed air or batteries.