Endure XC sock extra warm is a quartet of cross country skiing socks where each color is suited to different temperatures. The properties are differentiated by different yarn compositions and panels with different knitting structures and thicknesses. Since most of the heat loss occurs under the foot, the warmest version has a full terry sole and a high wool content. The second warmest version still has a high wool content, but is without full terrycloth, yet well suited for cold days. The next sock in the range has a lower wool content but this gives better sweat transportation on cold days where the thicker socks will feel too warm. The least warm version contains Coolmax yarn which offers a high degree of sweat transportation.