SmartWool Men's PhD Running UL Mini Socks wool Thanks to WOW Technology in high density impact zones, shock and abrasion are reduced. The 4-Degree Fit System keeps the sock in place. Micro height, ultra light cushion. 68% Merino Wool, 30% Nylon, 2% Elastic, washer and dryer friendly Men's sock sizes - Medium (fits US shoe size 6-8.5) Large (fits US shoe size 9-11.5) X-Large (fits US shoe size 12-14.5)