140 decibels is the equivalent sound of a jet engine and 4 times louder than the nearest competitor so you can alert cars, buses, lorry drivers & pedestrians to your presence. It has two sounds - a piercing 'road' mode and a lower pitched 'park' mode for cycle paths. The remote trigger means it is safe and easy to use when braking. It is easy to install and remove and the mount fits all bikes. Completely weather proof (although not submersible!)