Three-layer construction The top layer of felt wicks moisture away and keeps feet dry The second, heat-reflective layer prevents heat loss and directs it into the shoe The third layer, with small air pockets, acts as an insulating barrier to prevent heat from escaping and cold from entering under the shoe sole. The inner sole can be cut to size as needed. Sizes: M – for shoes sizes 40-43. L – for shoes sizes 44 – 46 XL – for shoes sizes 47 – 50