Don’t let the cold stop you from exploring the Great Outdoors. The Yaktrax Thermal Insole wicks away moisture, while redirecting heat back to your feet, keeping your feet warm in cold conditions.Made of recycled wool and felt, the Yaktrax Thermal Insole, is heat rated to -13°F and features Radiantex polyfiber. Radiantex polyfiber keeps heat directed at your feet, so you stay warm. One size fits most.