HEAT HOLDERS - Women's Original Ultimate Thermal Socks, One Size 5-9 us 91% Acrylic 5% Nylon 3% Polyester 1% Elastane 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.