Searching for a whistle for judges and ring crew that can be heard easily and that requires very little effort to blow? The Acme Survival Whistle fits the bill. It's S.O.L.A.S (Safety of Life at Sea International Regulation) approved and blows at half of normal lung pressure. It's also shatterproof and unaffected by water or weather. Works in sub-zero temperatures. Loud and far-carrying this whistle is used by NATO assault troops. Has a lower tone than the Acme Tornado Whistle. Size is 3 1/4"L x 3/4"W x 1/2"H. The long, narrow shape makes it very easy to hold in your hand without covering up the sound vents on the top and bottom.