Whistle Material: This emergency whistle is made of high-quality aluminum to ensure durability and safety. It uses high-frequency dual-chamber resonance, and the volume can reach 150 dB, and the sound can easily spread far. Advantages of the emergency whistle: This emergency whistle has an excellent airflow design, the surface is anodized for color formation, does not fade, and has a longer service life. It has no moving parts, no sound-damping parts, and is waterproof, allowing it to be used all day long, even in rainy days and wet weather. Versatile Uses: Suitable for trainers, survival, emergencies, dog training, and all outdoor activities such as hiking, soccer, sailing, water sports, gym, basketball, etc. It can also be used as a referee's whistle, dog whistle, a security guard's warning whistle, and a safety whistle for a person going out alone, especially for girls going out alone. Practical and Stylish: Each emergency whistle has a keychain that can be easily attached to a backpack or belt, or can be worn around the neck with a rope for a quick whistle. The appearance is simple and generous, convenient and practical, and has a high safety factor. Carrying a gold whistle and a silver whistle is also a great value!