FoxRiver X-Static Xpanse Fitted Crew Cut Socks 50% Polypropylene, 42% Nylon, 5% X-Static Nylon, 3% Spandex Made in US Fox River's patented Wick DryHealth Systemis designed to help keep feet dry and comfortable, no matter what the temperature. High-performance socks protect feet against cold or excessive heat and assist the foot's own temperature regulating function. Fox River uses a combination of natural and synthetic fibers to help keep feet dry and comfortable