Fox 40 sonik blast cmg whistle wlanyardsuperior performance combined with superior comfort ideal for large indoor stadiums and outdoor arenasadvanced science and technology makes this the most efficient whistle in its class the precise whistle chamber calibration assures pure frequency performance less effort crisper sound it emits distinct louder pitch without a lot of effort it has a superior clear loud blast that can be heard over long distances and intense ambient noiseincludes brea