Ladies/Womens Heat Holders - Ultimate Thermal Socks (1 Pair) Acrylic, Nylon, Polyester Size US 6-10, UK 4-8, EUR 36-42. With a thermal tog rating of 2.34 heat holders are the ultimate thermal socks. Average thermal socks have a tog rating of just 1.5. Thermal socks created using heavy bulk yarn, extra long terry cushioning and intense brushing process. Fiber 91% Acrylic, 5% Nylon, 3% Polyester, 1% Elastane