Hxst Stainless Steel Double or 3 Tubes High Frequency Loud Outdoor Whistle with Key Chain Strong and durable - Stainless Steel material ensures the whistle durable,it will last you a very long time Safety - The Whistle is made of Food Grade Stainless steel,Safety confirmed.You don't have to worry about it will cause harm to health 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/three tube design can make sounds up to 150 decibels.You can save 30% energy than normal whistle when you get the same db Wide range of application - Perfect For Referees Officials Coaches,Training,Sports,Teacher,Lifeguard,Life-saving ,Protection,Hiking,Camping,Wilderness survival,Emergency,etc