The Smartwool PhD® Pro Medium Crew men's sock features Indestructawool™ technology, a 4 Degree™ elite fit system, and body mapped mesh vents for breathability. The medium cushioned sock absorbs impact on the trail. It includes a Virtually Seamless™ toe and flex zone at ankle joint. The Achilles strap provides extra protection and warmth. The sock is made using imported yarns featuring 64% Merino Wool, 34% Nylon, and 2% Elastane. All Smartwool socks are proudly made in the USA, and carry a lifetime guarantee.