This jacket is about the art of dressing just right for cool conditions. We're talking about those days when you need some protection from the cool air but not enough to bring out the winter jacket. Overdress and you'll be sweating and get cold because you're wet. Underdress and you never fully warm up to enjoy the ride. The concepts behind the construction are fairly simple: wind protection on front-facing surfaces, highly breathable fabrics on back-facing surfaces, and all-around water repellency in case you get a few drops of rain. But what makes this jacket spectacular is how we executed these simple concepts. The wind protection comes from our GORE-TEX INFINIUM™ WINDSTOPPER® lightweight two-way-stretch fabric that moves with you while being so light you'll hardly notice it's there. This light wind layer is backed by a separate ProSecco Strada inner layer with a separate zip that can be opened independently for perfect ventilation control. The back is made from our Nano Flex Xtra Dry fabric that provides a good level of insulation yet has no membrane so allows for ample amounts of sweat to escape. The fit is close to body so there is no fabric flapping around, while the little details make the difference: easy-sliding YKK® zippers, reflective drain holes on the pockets, a lie-flat silicone gripper band around the waist. All these features are why this jacket is consistently named a favorite among Castelli staffers. We think it will be one of your favorites too.