The 1000 Mile Ultimate Lightweight Walking sock is a sock within a sock This double layer walking sock has a 100 Percent Tactel inner layer This inner layer stays with the foot, wicking away moisture, whilst the soft wool-mix outer layer moves with the shoe The lack of friction between the layers helps to prevent blisters and reduces wear with the unique combination of merino wool outer layer and the Tactel inner layer helps to maintain a comfortable temperature for the foot, HeelPower grips the heel keeping the sock firmly in place and helping to reduce irritation on the skin caused by the sock slipping on the foot Mid -calf length, ideal for 3 season walking in all boots