Prices are as marked; discounts may vary by color and size. Sales items are final and cannot be returned or warranted. High Performance Infrared Warmth. The Comp X is the warmest of the Performance Series, with a Channel Flex exterior for maximum stretch, and our exclusive Thermo Dry Celliant (TDC) infrared interior that penetrates deeper into the body's core for added warmth. The Comp X is completely sealed seams, with a one piece front and back panel design that is engineered to fit.