For extreme cold and challenging terrains, Smartwool Women's Mountaineering Extra Heavy Crew Socks are the perfect choice. These socks are made with a blend of merino wool, nylon, and elastane, providing superior insulation, moisture management, and stretch. The extra heavy cushioning and reinforced construction offer maximum comfort, durability, and protection against impact and abrasion. Whether you're mountaineering, ice climbing, or engaging in other high-intensity activities, these socks will keep your feet warm, dry, and blister-free.