Rab's Summit 400 Sleeping Bag is ultralight for summer trekking through the alpine, and it's protective just in case the clouds roll in. Its 650 fill down insulation has a hydrophobic treatment to stay warm in moist conditions. Rab wrapped this innovative insulation with an ultra thin Pertex Endurance fabric for air permeability, breathability, windproofing, and high levels of water resistance. The Summit 400 also features a snug, weight saving mummy shape, and the angled footbox prevents your feet from feeling too snug. There's also an anatomically designed 3D draft collar so you don't feel any cold breeze through the full length zipper. Rab added an internal stash pocket for your headlamp, and it included both storage and compression sacks for added convenience.