The Smartwool PhD Outdoor Medium Crew Socks are SmartWool's best hiking, trekking outdoor sock. Searching for a versatile wool sock that has it all? Look no further: the PhD® Outdoor Medium Crew offers fit, comfort and durability wrapped together in one smart sock. It features Indestructawool™ technology for ultimate durability in high wear areas, our 4 Degree™ elite fit system for a dialed fit, and our signature Virtually Seamless™ toe for extraordinary comfort in any trail shoe. Plus, the medium cushioning provides impact protection and ultimate comfort on the trail—making our PhD® Outdoor socks some of our best-fitting and most comfortable.