Cushioned Mouth Grip (CMG) provides superior grip and tooth protection. No moving parts to freeze, jam or deteriorate. Easy to blow and cannot be overblown; the most efficient whistle in its class. Chambers designed to self-clear when submerged in water for added convenience. Intensely clear sound that cuts through ambient noise, loud crowds and challenging environments. Easy to blow and cannot be overblown; the most efficient whistle in its class!. Chambers are designed to self-clear when submerged in waterIntensely clear sound - will be heard above ambient noise, loud crowds, the roar of engines, breaking waves and thundering gale-force winds. Sound will be heard up to a mile away.