Product Name: Dual-Hole High-Frequency Outdoor Survival Whistle, Emergency Self-Rescue High-Pitched High-Frequency Aluminum Alloy Lifesaving Whistle Material: Aviation aluminum alloy Specifications: 56*15mm Thickness: 8mm Weight: 12g The high-frequency double-tube whistle is a great outdoor accessory, compact, convenient, and easy to carry. Its design without internal beads allows it to be used even when water gets inside. When traveling outdoors, it can help you confirm your location, avoid getting lost, find companions, and provide other assistance. Box specifications: 2000 pieces, 38*32*31 cm, 21 kg The following is the universal whistle language: ● Short sound within one second；■ Prolonged sound for more than 3 seconds; The interval between commands should be 2-3 seconds, and the interval between commands should be at least 30 seconds. For example, if commands are sent repeatedly, there should be an interval of at least 30 seconds ●●■ Two short and one long, gather towards the direction of the whistle ●■  One short, one long; start off, speed forward; ●■■ One is short and two are long; someone is lagging behind, the front team waits for the back team ●●● Three short messages: Ask for help when encountering difficulties ●●●■■■●●● Three short, three long, three short. This is the internationally recognized SOS code