Feet Heaters Thermal Socks are an essential part of your Winter Wear. These socks are made of a high bulk Acrylic Yarn with excellent thermal qualities. Each sock has been brushed inside for an ultimate comfort and luxurious feel. The brush process is designed to trap warm air against the skin for an extra warm and cosy feel. Ideal for the coldest of wintry days and nights, when your feet can be the first to feel cold. Because of Feet Heaters specially brushed insides and thick bulk yarn, these socks have a Tog rating of 2.2 which is nearly 5 times warmer than a normal cotton sock.