Fox 40 CMG Classic Official whistle 9601-00089603-0008 The FOX40 Official Classic is the world's #1 professional referee whistle . It's used by 90% of referees worldwide. It's also a great tool for all coaches and is also very useful for teachers. The whistle is equipped with a mouthpiece for increased protection and oral hygiene, as well as more reliable sound control. The FOX 40 CMG Official Classic has a unique sound thanks to its ball -less design. It is constructed of plastic. It's perfect for referees and coaches of all levels. It's reliable in any situation where it needs to be heard above ambient noise, roaring engines, and wind. Properties: Sound pressure level: 115 dB. Two chambers facing each other. Silicone mouthpiece. No moving parts. String color-matched to the whistle Whistle color: black String included: Breakaway – elastic drawstring with an adjustment system and snap closure at the neck, which allows for quick release in case of emergency. The FOX40 is the official whistle of the NBA , NHL , NBL , NCAA , FIBA , FIVB , and other federations. The FOX40 is a ballless whistle with internal channels that produce a very loud sound. It is also used by law enforcement agencies. It is very useful for sailing, windsurfing, mountaineering, and other areas where a loud signal is needed. In the US and Canada, people use it as a safety whistle .