A great choice for summer mountaineering trips or other adventures involving colder temperatures, the SmartWool Trekking Heavy Crew sock provides a haven of comfort for your feet. Heavy full cushioning surrounds the foot, a nice buffer to have when wearing the heavier, stiffer footwear usually associated with extended alpine excursions. The SmartWool fibers also have a lot to do with the fabulous comfort experienced in the SmartWool Trekking Heavy Crew sock. They have a very small micron diameter, between one-tenth and one-third the size of a human hair, making for a very soft, comfortable feel. And equally important, these same fibers move perspiration moisture at a fast clip, even while still in the vapor stage so the feet stay dry throughout the day.