Despite their small size, the whistles produce a loud sound, ensuring they're heard in emergency situations, be it in the wilderness or an urban environment Aluminum Alloy Durability: these emergency whistle keychains are built to last, made from a sturdy aluminum alloy that ensures the of each piece; This quality material ensures the whistle is resistant to damage and wear and tear, keeping it in working order for years; The whistle's attractive beautiful color gives it a professional aestheti Specification: Universal Whistle Language: Short notes (one second), long notes (more than 3 seconds). The interval between whistles is -3 seconds, and the interval between commands is more than (for example, repeating commands requires an interval of more than ). Two Shorts and One Long: Gather in the direction of the whistle. Short and long: set off and accelerate forward. One short, two long: someone falls behind, the front team waits for the back team. Three Shortcomings: help when encountering difficulties. Three short, three long, and three short: This is the internationally recognized SOS code. Material: Aluminum alloy colour: Multicolor Package Contents: 10 x whistle Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.