Widely Used: This survival whistle is a great tool for outdoor activities, such as camping, fishing, hiking, hunting, emergency rescue. Loudest sound, dual tubes can go up to 120 decibels, can be heard from a distance. . Signal: If you lose contact with your friends in the mountains and the phone has no signal, you can whistle then stay where you are and wait, wait for your friend to save you. . Solid and durable: Aluminum alloy ensures the durability of the whistle, safety is confirmed. The whistle does not have a built-in pea, so it will not mold or produce bacteria from the pea. You can use it in any dusty or dirty water environment. Small and light: Can be easily carried on a keychain, convenient and practical, can be attached to your backpack, belt, which can be attached to a lanyard or key when needed. Note: The data is manual measurement, please allow 1-25cm error, due to differences between light and screen, there will be a certain color difference, the specific received in kind shall prevail.