Smartwool Men's PhD Outdoor Light Crew Socks 63% Merino Wool, 34% Nylon, 3% Elastane Light Cushion: Light cushioned sole, shin and calf for impact absorption. 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. Knit in USA of Imported Yarn Style: SW0SW044 Sock Height: Crew - 8.5" overall height - Flat knit durable toe seam Strategically placed mesh ventilation zones provide ventilation for temperature and moisture management