The most important layer in a thermal body system is that one closest to your skin. Heat Holders Microfleece Base Layer Bottoms, with their specially developed lightweight microfleece construction, have a heat retaining brushed surface and an excellent warmth to weight ratio, TOG rated to 0.61. However, the microfleece also allows the bottoms to remain highly breathable, allowing moisture to escape and keep the wearer dry and warm. Heat Holders Microfleece Base Layer Bottoms are designed for a comfortable fit thanks to the innovative multi-directional stretch knit and flat-locked seams, which minimise bulk for a non-chafe fit. (11/14) SOCKSHOP Heat Holders Men's 1 Pack Microfleece Base Layer Bottoms in Black Size: Large