This multi-functional clothing has everything one could ask of a base layer. XWARM regulate your temperature while keeping you warm and dry even in extreme cold. The material consists of an inner layer of channel knitted polypropylene which transport humidity away from the body and to the outer layer, where it is absorbed by the merino wool. Recommended temperature -20°F to -5°F. Keeping you warm and dry even during stationary work in the biting cold.