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 approach here. You'll wear this jersey on cool days, so we've given it a brushed fleece backing but kept the fabric stretchy for a great fit. Since you're using it 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. We think a jersey like this should be pure function, so you've got our three spacious rear pockets, silicone gripper elastic, and easy-sliding YKK® Vislon® zipper.