Hxst High Frequency Aluminum Alloy Double Tubes Whistle with Keychain Strong and Durable - Made of premium aluminum alloy material,it will last you a very long time Light and Portble - You can put it in a bag and pocket,or hang it on a keychain and backpack zipper Good Environmental adaptability - The whistle has no built-in pea ,so it will not mold and breed bacteria because of the pea.You can use it in any dust or dirty water environment Very Loud - Double tube design can make sounds up to 118 decibels.You can save 30% energy than normal whistle when you get the same db Multi Purpose Whistle - Perfect For Referees Officials Coaches,Training,Sports,Teacher,Lifeguard,Life-saving ,Protection,Hiking,Camping,Wilderness survival,Emergency,etc