The Smartwool PhD® Outdoor Light Mid Crew features a versatile, multi-sport design. The lightweight mid-crew includes Indestructawool technology for ultimate durability, 4 Degree™ Elite fit system for a dialed-in fit, and Virtually Seamless™ toe to offer extraordinary comfort in any trail shoe. The Mesh ventilation zones provide optimum moisture management and maximum breathability. It is made of 60% Merino Wool, 37% Nylon and 3% Elastane. All Smartwool socks are proudly made in the USA, and carry a lifetime guarantee.