The Mini horn with the Maximum sound. Just a touch of your thumb produces a piercing blast that can be heard up to half -mile over land and a mile over water. Palm-size convenience with unlimited uses from casual small craft signaling to personal protection. 100% ozone-safe-non-flammable. Compact- only 4-1/2" tall. Stainless steel,non-corrosive diaphragm. Guaranteed unbreakable. Meets U.S. Coast Guard recommendations for boats up to 39 (12 meters). Refills 2-packs available. No need to worry about batteries.