The Classic Fox 40 Safety Whistle Is The Original And Still The Standard Choice For Rescue Professionals. Sometimes You Have To Be Heard To Be Rescued. The 3-chamber Pealess Design Has No Moving Parts To Freeze, Jam Or Deteriorate. Easy To Blow And Cannot Be Overblown. The Harder You Blow, The Louder The Sound. Chambers Are Designed To Self-clear When Submerged In Water. Sound Will Be Heard Up To A Mile Away. A Whistle Is Vital For Signalling Above The Sound Of Surf And Whitewater. Remember, In Most On-the-water Situations A Sounding Device Like A Whistle Is Required By The Coast Guard. We Recommend Against Attaching The Whistle To The Zipper Pull On Your Life Jacket. That Can Result In Accidental Unzipping.