The 1000 Mile Double Layer Trainer Liner Running Socks feature a Tactel inner layer that stays with the foot, wicking away moisture, while the outer layer moves with the shoe. This design reduces friction between layers to help prevent blisters and reduce wear. Key features include top venting for superior breathability, arch bracing for extra support, and Heel Power technology. The outer layer is made from 54% Cotton, 44% Nylon, and 2% Lycra. The inner layer is 100% Tactel. Sizing is based on UK shoe size.