TheAcme 58 Thunderer Brass Whistle is a large size whistle with a deep tone and a square mouthpiece. Waterproof speed pea with easy to blow instant response. Today Acme whistles are recognized as some of the finest whistles manufactured in the world today. In 135 years, Acme developed and patented over 40 different whistle designs. Toughest build quality and perfection to finish. The professional sound and professional look. Pro model. Large, lead-free metal pea whistle with a deep tone. Big, deep, far carrying sound. Recommended for coaches referees.