You don’t even have to blow this compact ELECTRONIC POCKET WHISTLE. Just push a button. Emits a loud 120db whistle for as long as you push the button. Useful in various situations such as sporting events, a locator in emergencies (earthquakes, collapsed buildings), as referee whistle, traffic use for police, military training, dog handling and as a safety alarm for crime prevention. Uses 4 LR44 batteries (included). 4 inches long.