You don't need a doctorate degree to see that wearing the Smartwool PhD Nordic Medium Sock makes a whole world of difference when it comes to comfort and support. This newly updated sock features Smartwool's Indestructawool, which consists of a highly durable merino wool knit that not only provides dependable temperature regulation and moisture management, but also assures exceptional longevity. Meanwhile, the 4 Degree Elite fit system ensures a secure fit that won't slip or bunch in your boot so you won't have to stop to make adjustments or deal with painful blisters. Ventilation zones offer breathability where you need it most, and the Nordic boot-specific height eliminates unnecessary material.