DESCRIPTION: This whole sole warmer runs the full length of the foot, so it warms the entire foot, not only the toes, for up to 6 hours. It’s ultra thin and air activated, slips into a boot or shoe, and contains activated charcoal to absorb odour. Size M/L is made for men’s shoe sizes 8 and up and women’s shoe sizes 9 and up, and it fits right into winter survival kits next to thermal socks.