In winter sheepskin is a natural insulator trapping airspaces between the fibers capturing your body heat. The free flow of air between you and the sheepskin fibers is a comforting change to the clamminess of lamented pigskin, cowhide and synthetic fleece materials found in cheep boots often mistakenly marketed as "Sheepskin Boots". Additionally, sheepskin contains lanolin, which will moisturize your feet for additional comfort.