The Ss. rallytrekkingJersey with Base Layer represents the absolute pinnacle of Assos' mountain jersey technology. The rally trekking jersey is light, anatomically pre shaped and protective. This moisture wicking top layer is specifically designed to keep you cool when partnered with the included Assos Skinfoil baselayer, which uses moisture to either insulate or cool, depending on outside temperatures. For its rally trekking jersey, Assos uses a synthetic stretch fabric. This smooth polyester material works to transfer moisture at varying rates. When your body is hot, and your perspiration levels are high, the material reacts by accelerating moisture transfer from your skin to the fabric's surface, where it dries quickly. Inversely, when your body cools down, the opposite results, where the evaporation process slows down, using body moisture as a means of retaining warmth. Assos includes the appropriately sized skinFoil S7 baselayer with the Ss. rally trekking jersey. This baselayer perfectly complements the jersey. Not only does it augment the jersey's temperature regulation system, but it adds protection from the sun's harmful UV rays.The jersey was made with a regular, body mimicking fit that follows the contours of your torso. Of course, this jersey, like all Assos jerseys, has been designed to accommodate the body within the cycling position. Accordingly, you'll find that the fit feels tight and oddly contoured while standing. However, the moment that you stretch to the hoods or get into the drops, you'll feel that signature Assos click, and your ride will be guaranteed to be absent of any bunching, chafing, or pinching.The back of the jersey is made with an open mesh, which acts as a heat exhaust during hot weather rides. Because of this, however, it provides less sun protection. Again, Assos urges you to wear this jersey with the included baselayer during rides where the sun is a factor.