For extreme cold weather and high-altitude adventures, Smartwool Women's Mountaineering Extra Heavy Crew Socks are a top choice. These socks are made with a blend of merino wool, nylon, and elastane, providing exceptional warmth, moisture management, and durability. The extra heavy cushioning and reinforced construction offer maximum comfort and protection in harsh conditions. Whether you're climbing mountains or braving the elements, these socks will keep your feet cozy and dry.