Outside layer nylon and lycra spandex. Middle layer waterproof MVT (moisture vapor transpiration) allows perspiration to escape while not allowing water to penetrate. Inside layer DuPonts coolmax yarn, this combination provides a soft, flexible, stretch to fit sock suitable for a whole lot of uses. The seamless design provides the ultimate in action performance and comfort. Made in USA. GSA Compliant. ISO 9001:2000 Quality Certificate. SealSkinz. Black color.