Thanks to the Hydrostop shaft, these are a great choice for cycling, where water tends to run down your leg or tights towards the socks. Silicone stripes help prevent water ingestion, and the socks have a 100% waterproof membrane. - Warm weather model: thinner than most Sealskinz products - Flat lock seams for reduced chafing - Surface: 94% Nylon, 6% elastane - Hydrophilic, breathable, waterproof membrane - Liner made of 75% bamboo rayon, 22% Nylon and 2% elastane plus 1% TPU - Sizes: - S = 36 - 38 - M = 39 - 42 - L = 43 - 46 - XL = 47 - 49 This product used to be called the "WP Warm Weather Ankle + Hydrostop".