Thermohair socks are made of 75/25 kid mohair/nylon yarn. The most durable sock you will ever wear! There is no tougher natural fibre that can take the continual foot rubbing that occurs when you walk. Mohair is very insulating, protecting your feet from the cold and sub-zero outdoor weather. Over the years they have been worn up every major peak, including Everest, and have been worn in both poles. They are the best socks for those working in steel toed boots or playing in the cold outdoors or for those who suffer from cold feet due to health issues. Scuba divers wear them in their suits to keep their feet warm in the icy waters.