When we're planning on sleeping in tough conditions but aren't interested in carrying a tent, we make sure to stick the Rab Alpine Bivy in the pack first. It weighs only a pound and packs down to the size of a water bottle, so we never have to leave essential gear out of our pack to bring it along, and it zips up all the way to offer full protection from the alpine elements. The eVent waterproof and breathable membrane and 3-layer DVStorm fabric keep water out and prevent condensation from building up inside, while the tough nylon floor stands up to rough ground when sleeping in less-than-perfect conditions.