Built for trail runs in changeable alpine conditions, the Airshed Pro Pullover from Patagonia is a fast-drying, breathable and, perhaps most importantly, ultralight midlayer. It's constructed from a stretch polyester woven ripstop that's been treated with DWR for protection from light showers. And while the fabric offers exceptional breathable qualities on its own, the style is nevertheless equipped with a two-way zip, allowing rapid-fire heat dumping when efforts are intense. Other details include a stretch-knit hood that moves naturally and won't impede your peripheral vision, and gusseted underarms for excellent mobility.