The RFL is the lightest sock we make for the hill, but it's no lightweight. The RFL is totally Darn Tough. This simple go-to sock is designed specifically for skiers and riders looking for an incredibly lightweight sock without compromising on durability or fit. Over-the-Calf height is ideal for skiing and riding in deep conditions while Ultra-Light Merino Wool provides legendary warmth without the bulk. And since Merino Wool is naturally antimicrobial this sock repels bacteria and odor. If only everything in life was this simple. Still made in Vermont. Guaranteed for life.