Material High quality plasticSize 70mm*27mm*7mmApplication When you travel outdoors, it can help you to confirm your location, avoid getting lost, find your partner, etc. Features (1)Made of high quality plastic, light and easy to carry, easy to use.(2)The whistle has three holes, each hole sound is different.(3)The whistle comes with a hanging chain, which can fix the whistle for easy movement. Instructions for useCan be used for outdoor survival, training purposes. (In the wilderness in distress, wilderness rescue survival, the whistle plays a big role! Although we have better communication equipment instead of whistles, but the role of the whistle still can not be ignored. Once the modern equipment without the supply of electricity, signal shielding area, orientation determination, water distress, etc., is when the whistle comes into play.)The following is the common whistle language● Short sound (within one second) ■Long sound (more than three seconds)Intra-command whistle interval of 2 - 3 seconds, interval between commands of 30 seconds or more (e.g. repeated sending of commands requires an interval of 30 seconds or more) ●●■ (Two short ,One long) Gather in the direction of the whistle●■ (One short, One long) Departure, acceleration●■■(One short,Two long) Someone falls out of line, the front line waits for the back line●●●(Three short) Seek help when in trouble●●●■■●●●(Three short,Three long,Three short) universal SOS code