The thermal jersey is the first step into cool-weather clothing, where Castelli has set the standard for what clothing can do. We've taken the same standard-setting approach here. This jersey is for cool days. It's got a stretchy fabric with a brushed fleece backing for warmth and great fit. Since you'll use this in conditions that aren't cold enough for a jacket, we've engineered the fabric to let some air in so you don't overheat. A jersey like this is about pure function; that's why along with a great fabric and fit we've provided three back pockets, a silicone gripper elastic, and an easy-sliding YKK® Vislon® zipper.