More than a decade after we introduced our R1 fabric, it remains a favorite the world over for good reason: It stretches, breathes, wicks and warms with ultimate efficiency. The full-zip iteration only enhances its range, whether worn as a midlayer or a lightweight jacket. The finely tuned high/low interior grid polyester fabric (Polartec Power Grid an exclusive to Patagonia) is now even lighter and more breathable. With its technical fit and durable fabric, it squashes down to practically nothing in your pack. A soft, kissing-welt zipper garage at the chin gives next-to-skin comfort, the redesigned simple cuffs keep a low-profile, two zippered handwarmer pockets sit above harness line, and offset shoulder seams steer clear of pack straps.