HEAT HOLDERS - Men's Thermal Fleece Ribbed Knitted Winter Hat 3.4 Tog - One Size 100% Acrylic machine washable at 40 degrees Heat Holders Yarn - Specially developed thermal yarn provides high performance insulation against cold with superior moisture breathing abilities. Heat weaving lining - HeatWeaver insulation is a plush fur-like thermal lining that maximises the amount of warm air held close to the skin. 3.4 Tog rating - the tog rating is a measurement for the thermal ability of a garment. 3.4 tog is considered to have very high thermal ability. Heat Holders rib construction - Our stretchable rib construction contours around the natural shape of your head for improved fit, warmth and comfort. Heat Holders - Best seller since 2010, providing a wide range of winter thermal products that we provide in the sock snob online amazon store