The Smartwool PhD™ Outdoor Light Micro is an ankle-high powerhouse made for mileage. It features Indestructawool™ technology for ultimate durability and the 4 Degree® elite fit system for a dialed fit. It also features light cushioning to offer impact protection on the road or trail, while the Virtually Seamless™ toe offers more comfort in a trail shoe. The mesh ventilation zones provide optimum moisture management and maximum breathability. It is made of 60% Merino Wool, 38% Nylon and 2% Elastane. All Smartwool socks are proudly made in the USA, and carry the Smartwool Promise.