The SmartWool PhD light cycling socks are designed for distance road riders in any weather condition, however they also versatile enough to wear while mountain biking. The sock consists of 76% Merino Wool, 21% Nylon and 3% Elastic. All Merino Wool products naturally control odor and moisture. You'll find high density SmartWool Duroyan in the heal and ball/toe area of the foot. There is also a light cushion on the sides of the sock, where the bike shoe rubs against the foot while pedaling. All seams are flatlock stitched for extra comfort.