Simply hold them in your hands, stuff them in your sleeping bag, or keep them in your pockets for up to 18 hours of cosy warmth. Both safe and easy to use, the Yaktrax Hand & Body Warmers are an all-natural solution to dealing with the cold. Once opened and exposed to oxygen in the air, these disposable warmers begin working in just minutes.. Yaktrax Warmers are the ideal choice for outdoorsmen, winter athletes, spectators, and anyone who works or plays outdoors. Also ideal for keeping warm when camping, hunting, fishing, skiing, watching sports and outdoor events, and more._·     1 Warmer Per Pack·     Up to 18 Hours of Heat·     Safe·     Air-Activated·     Odourless Heat