Two outer chambers create separate omni-directional frequencies, while the center chamber with pea creates staccato sound, critical for rescuers to discern whistle over environmental noises such as howling wind, rushing water, emergency vehicles etc. Comes with fastener for key ring and backpacks. Trapped or injured victims in the aftermath of a disaster quickly become hoarse from yelling or from debris breathed in through the air. While injuries may limit your ability to shout for help, if you can breath you can easily blow this whistle. Ideal to have in the car or taped under your work desk in case of emergency. Also a great safety device to carry with you for personal protection. Specifications: - High impact ABS plastic - Length 70 MM - Width (at widest point) 35 MM - Loudness - Up to 118 - 120 dB - Universal locking safety clip included.