Smartwool made the Men's PhD Pro Approach Light Elite Crew Sock with professional mountaineer Conrad Anker for long, technical treks to faraway alpine objectives. Merino wool grants this sock with lightweight thermal regulation suitable for summers in the alpine, and it's part of Smartwool's Indestructawool for enhanced durability. The sock has a 4 Degree Elite Fit that maintains a seamless feel between sock and treakking boot.