Terramar Size Chart The 2-Layer Authentic Thermal Bottom is the workhorse of the Terramar line. This soft, versatile piece will protect you while skiing on a cold winters day or keep you comfortable while blowing snow or splitting wood in the driveway. The dual-ply midweight microfiber fabric traps plenty of air to keep you warm, dry and comfortable throughout the day. If you are a busy guy you don't want to worry about your layers. The Authentic Thermal gets it done. Features: - The dual-ply microfiber fabric traps air and allows breathability - ec2 QWIK-DRI tech is fast wicking and drying - Anti-odor - Midweight warmth - UPF rating 25+ - Flat seam construction for comfort - 100% Micro-Polyester