When you 've got lots of miles to cover but only want the minimum between your foot and boot, the PhD Outdoor Ultra Light Crew by Smartwool is the perfect trail companion. The sock is made from Indestructawool technology – a weave of merino wool reinforced with nylon – that has 5% nylon for extra stretch. It features Smartwool’s new Shred Shield technology for reduced wear from toes. The 4 Degree elite fit system for a more dialed-in fit. Activity-specific mesh zones for additional breathability, this sock was built for mile after mile of trail.