Electronic Pocket Whistle does not require you to blow this, just push a button. The electronic pocket whistle emits a loud 120 DB whistle for as long as you push the button. The electronic pocket whistle is useful in various situations such as sporting events, a locator in emergencies, referee whistle, traffic use for police, military training, dog handling and as a safety alarm for crime prevention. The whistle is 4 inches long and uses 4 LR 44 batteries which are included. Size 4 1/8 x 5/8 inches.