The RFL is the lightest sock we make for the hill but it's no lightweight. The RFL is totally Darn Tough. Coveted by skiers and riders for its True Seamless construction, the RFL provides plenty of warmth and a smooth, streamlined fit. This sock just disappears when you put it on. Nothing feels better than the warmth Merino Wool provides when the mercury drops. Ideal for skiers and riders who are looking for a sock that interfaces seamlessly with their boots and allows them to feel the terrain underfoot. And since Merino Wool is naturally antimicrobial this sock repels bacteria and odor. Still made in Vermont. Guaranteed for life.