The Castelli Perfetto RoS Vest is a warm, windproof, and breathable vest for added comfort during spring and fall rides. It uses GORE-TEX INFINIUM WINDSTOPPER fabric on the front of the vest with Nano Flex stretch woven fabric on the back to keep out wind and water. A top and bottom opening YKK Vislon zipper provides you with superior ventilation and is so lightweight that it easily packs into a jersey pocket when the vest is no longer necessary.