SmartWool Men's PhD Ski Ultra Light Socks - Past Season 55% Merino Wool, 41% Nylon, 4% Elastane Knit in USA Sock Height: Over the Calf - 14" overall height PhD: Built for Performance in the Highest Degree. 4 Degree Elite Fit System: Uses two elastics for greater stretch and recovery to keep the sock in place. Reliawool: Patented ReliaWool technology in high impact areas provides superior durability. Mesh Venting: Men's-specific mesh ventilation zones provide additional breathability and moisture management. Ultra Light Cushion: Non-cushioned sole and leg for a close fit in tight-fitting performance boots. Virtually seamless toe Knit in USA of Imported Yarn Style: SW0SW003