The Rab Men's Windveil Jacket is an ultralight windbreaker that you can stash in a running vest and zip on once you reach the windy ridge. Its Pertex Quantum Air shell resists water as well as wind, and it maximizes breathability to an air-permeable level. Unlike most breathable shells which breathe only after you start sweating, air-permeable shells like the Windveil begin to breathe the minute you put it on. An ideal layer for mountain running and hiking, the Windveil is the perfect partner for blustery days on the mountain.