The 1000 Mile sock is a sock within a sock. The inner layer stays with the foot, whilst the outer layer moves with the shoe, thus eliminating friction on the skin & reducing wear. The unique mixture of fibres helps to keep the foot dry & blister free. The unique Tactel inner layer wicks away perspiration to the moisture absorbing outer layer, keeping the feet dry. The combination of fibres keeps your feet warm & comfortable in the most extreme conditions.