VANGUARD sole construction Cushioned polyurethane midsole VIBRAM FIRE & ICE Sierra outsole for superior traction in icy conditions 200g Thinsulate insulation Gore-tex waterproof fabric bootie Perfect for cooler conditions, the 770 features 200 grams of Thinsulate insulation and a GORE-TEX waterproof bootie which allows your feet to stay warm, dry and comfortable. Another special feature is the Vibram FIRE & ICE outsole used that is made of a special rubber compound that does not harden in cool temperatures to provide better traction in icy conditions.