When you're running often or running long distances, the Smartwool PhD Run Ultra Light Low Cut Sock keeps your feet comfortable. Well ventilated and made with a merino wool blend, these socks will have your feet feeling free thanks to the temperature regulating, moisture wicking, and fresh-smelling ways of merino wool and mesh ventilation zones. Plus, with Indestructawool and Shred Shield technologies, the socks withstand many, many miles of wear.