The Black Diamond HighLine Stretch Shell is the type of layer that has a place in our pack every time we head for higher elevations, perfect for windy early morning starts and stormy afternoon descents. The BD. dry membrane is exceptionally waterproof and breathable, keeping us comfortable while we tote a heavy pack up steep mountains and deflecting snow and wind as we work our way up the skin track. The stretch fabric gives us our full, natural range of motion, and since it packs down small, we can keep it in our pack and be ready for anything the mountains throw at us.