The Theo Socks are an ultra thick sock which we affectionately call the ""mega"" sock. Made with Peruvian alpaca, one of the most luxurious fibers in the world. Peruvian alpaca is hypoallergenic, soft, and silky, and alpaca fiber production is one of the most sustainable fiber production processes. Alpaca is a natural technical fiber, it has a breathable, unique thermal quality that allows air circulation for the foot to prevent sweating in warm weather, and in cold weather, contains heat for warmth. This sock is perfect for keeping warm at home in the cooler seasons, adventuring in the great outdoors, and wearing with boots in the deepest days of Winter! "