Winter boot for all cold weather conditions Comfortable fur lined winter boot, cold insulating down to -15°C Extra traction outsole profile for excellent grip Cold insulation Purofort® boots prevent heat loss and offer outstanding thermal properties. Due to the unique recipe and molecular structure, all Purofort boots assure excellent cold insulation down to -20 °C. And even down to -50 °C in case of Purofort Thermo+ boots. Purofort boots are classified as CI, meaning that the temperature decrease measured at the upper surface of the insole does not exceed 10 °C after 30 minutes.