The Authentic - Natural Warmth and Comfort. The Authentic two layer garment has been specifically engineered with our ColdPruf Insulation System to trap air between the layers of fabric to provide a natural warmth shield. The Outer Layer of Merino Wool, nature's warmest fiber, blended with Combed Ring Spun Cotton and Nylon and paired with 100%Combed Ring Spun Cotton on the Inside, offers the desired warmth and comfort in very cold to extremely cold weather conditions during low to medium activity.