Smartwool PhD Nordic Ultra Light Sock Other Indestructawool technology features a wool-based, patent-pending yarn and construction method for exceptional durability and comfort. 4 Degree elite fit system uses two elastics for greater stretch and recovery to keep the sock in place Mesh ventilation zones provide optimum temperature regulation and moisture management 200 needle construction provides highest knit density while maintaining ultra light weight Virtually Seamless toe; 8.5" overall height