x-bionic trek x ctn socks dark green navy blue black The x-bionic trek x ctn socks have a set of pads placed on the heel and which offer a natural movement of the feet. Optimized air channeling system designed in fine mesh fabric that allows continuous air circulation to regulate the temperature around the foot. features: - a two-piece pad protects the Achilles tendon from pressure and impact - chafing and blisters are avoided. Materials: - 48% polyamide - 30% cotton - 20% polypropylene - 2% elastane.