Unless you're an anomaly, your feet will sweat during activity, so the SmartWool PhD Outdoor Ultra Light Micro Sock is designed to breathe and offer cooling, quick-drying comfort no matter how rigorous your favorite outdoor activity can get. A 4-degree Elite Fit system uses two elastics for greater stretch and recovery, keeping this sock in place, while the patented ReliaWool technology in high-impact areas improves durability and support. Plus, moisture-managing properties pull sweat away from your skin to prevent the dreaded swampfoot.