It’s time to take “burr” out of your running vocabulary. Stride out in our PhD® Run Cold Weather Mid Crew. A Merino blend and mesh zones designed for runners help keep your feet warm during long winter runs. With a run-specific profile and our 4 Degree™ elite fit system, with two elastics for greater stretch and fast recovery, these socks stay in place at every turn and up every hill. See below for sizing information.