YakTrax Foot Warmer Insoles - 20 Pack

2 WARMERS PER PACK UP TO 5 HOURS OF HEAT SAFE, NATURAL HEAT ENVIRONMENTALLY FRIENDLY AIR-ACTIVATED ODORLESS AVAILABLE IN S/M AND M/L 6 BOXES (120 PAIRS) PER MASTER CASE Yaktrax? Foot Warmers are a safe, easy, and all-natural solution to dealing with cold feet. Once opened and exposed to oxygen in the air, these disposable but environmentally-friendly warmers begin working in just minutes. Slide them inside your boots to create a warming barrier for your feet that lasts up to 5 hours. Yaktrax Warmers are the ideal choice for outdoorsman, winter athletes, spectators, and anyone who works or plays outdoors. HOW IT WORKS When exposed to oxygen in the air, the iron filings inside the pouch begin to oxidize creating a rapid rusting process which in turn produces residual heat. Salt acts as a catalyst, while carbon helps to evenly disperse the heat. Vermiculite acts as an insulator that helps prevent the heat from dissipating too quickly.