Heat Holders - Womens Thermal Knee High Winter Boot Socks 4 Colors 91% Acrylic, 5% Nylon, 3% Polyester, 1% Elastane Machine Washable Heat Holders Yarn - Our Specially developed thermal yarn provides high performance insulation against cold with superior moisture breathing abilities. Heat Holders Loops - Innovative knitting tehnology produces our unique, extra long looped cushion pile to hold in more warm air, increasing the TOG rating. Heat Holders Brushing - Finally, our expert brushing process maximises the amount of warm air held inside each sock for total warmth and all day comfort. Heat Holders are Scientifically tested to be over 7x warmer than a basic cotton sock! Heat Holders Tog rating being 2.34 whilst a basic cotton sock only measures at 0.33 Tog. Heat Holders Boot Socks - These Socks are absolutely perfect for when you have to spend those cold winter days outdoors, whether your in wellies or boots, these socks will fit perfectly.