The Thermoball Traction slippers use the same ThermoBall insulation fiber you'll find in many The North Face puffer jackets. You can choose between just stepping on the heel for super easy use, or wearing the heel as usual. A great choice for cabin and tent accommodation - also useful when strolling around camp. - Surface fabric: recycled ripstop polyester - Recycled fiber ThermoBall Eco insulation - Warm fuzzy fleece liner - Outer sole contains more than 20% recycled rubber Men's US sizing.