This mid-weight, duo layer crew, consists of a fully synthetic inside and Merino blend face. Our bi-layer construction, creates an air pocket in-between both layers for additional insulation and thermal regulation. The synthetic backside, helps to push sweat and moisture vapors to the surface to keep the wearer dry and comfortable. Merino wool, is natures best at thermal regulation and odor control. Our Merino wool is blended with nylon for an added degree of durability. Great on its own or with the Ultra Merino Pant.