Hammerhead Classic M4:9 Whistle (Black) US Patented - Patent No. 7,428,878 Designed for the safety of your ears and to help prevent hearing damage caused by prolonged whistle use Waterproof Pea that is specially weighted and designed to propel saliva, debris, etc. out of the whistle chamber Pea WON'T JAM! Thanks to the Hammerhead PEA, you won't ever have to worry about jamming peas! The Hammerhead whistle design sends sound FORWARD and FURTHER!