Description of SmartWool PhD Running Light Mini Socks The new PhD running mini crew features a quarter-top sock with high density SmartWool cushioning in the critical impact zones for added protection and durabilty, Combine those features with the new SmartFit system and you've got the ideal sock for any running event that requires great fit and all day SmartWool comfort and performance. Features: 62% wool, 35% nylon, 3% elastic