TVX - Engineered to keep you dry! TVX stands for Total Vapor Exchange. This 100% Polyester fabric is made up of two different types of yarns, each with its own characteristics, so that moisture is moved efficiently away from your skin. A loose-spun yarn on the inside of the fabric soaks up moisture quickly and moves it to the outside surface. A second tighter-spun yarn on this outer fabric surface collects the moisture and allows it to evaporate. The inner surface of the garment always feels dry, even if the outside is wet. Try putting a few drops of water on the inside of TVX, then feel the outside. You will feel why you'll stay cool and dry on the bike.