Engineered with a 4 Degree(R) elite fit system, Indestructawool(TM) technology in high-wear areas and medium cushioning, the PhD(R) Outdoor Medium Pattern Crew Socks don't need a degree to prove that they're some of the smartest (and most comfortable) adventure socks out there. . . . 64% Merino wool, 34% nylon, 2% elastane. . Indestructawool(TM) technology in high-wear areas for increased durability. . 4 Degree(R) elite fit system provides enhanced stretch and recovery for stay-put comfort. . Mesh ventilation zones for moisture management and breathability. . Medium cushioning absorbs impacts. . Virtually Seamless(TM) toe provides irritation-free comfort. . 8.5 in. overall height. . Knit in USA of Imported Yarn. .