The KEEN Dura-Zone Medium Crew Utility Sock is designed to keep your feet fully protected for the long haul. Dura-Zone high-tenacity nylon fibers – weight for weight stronger than steel – are blended into the heel and toe area for ultimate comfort and durability. Breathable panels, cushioning, and articulated support in all the right places offer even greater comfort. Right-angle Heel Hold cup construction provides a secure, natural fit. A Wunderseam seamless toe in the flex zone helps eliminate bunching, while the left and right foot design further optimizes the fit. 66% Merino wool, 15% nylon, 14% polyester, 3% Dyneema, 2% Lycra spandex fabric. Built in the USA.