Lining up 12 pitches in a day is a serious endeavor, and while you'd prefer to do it in perfect weather sometimes that's not just how things go, so you need an ultra light rain shell like the Arc'teryx Alpha FL Men's Jacket. The lightest Gore Tex Pro jacket that Arc'teryx makes, the FL Fast and Light, if you were wondering is the speed demon of the climbing and alpinism oriented Alpha series, with a lightweight 3 layer design, waterproof and breathable membrane, and taped critical seams to keep you dry without any extra bulk. Unlike average shells, the FL is designed specifically with climbers in mind. It has a trim fit to eliminate any extra material, and an e3D ergonomic design that's articulated in all the right places to facilitate climbing movements The slim profile also makes it easy to see your harness, so you don't waste time and energy trying to grab piece of gear from it, while the removable HemLock foam hem inserts keep your jacket from sliding up under your harness and leaving you exposed. The helmet compatible StormHood adjust with a single handed pull, and the entire package stuffs into the zippered, harness compatible chest pocket and clips onto your harness with a webbing loop, making it easy to carry and quickly accessible when the clouds gather.