By the way the integral designs Salathe, not the lightest bivy
but it does have extra features to keep more dry, the middle of the bivy can open up and fold down during good weather or under a tarp also in worse weather on the sides you can open up under the zipper flaps and get cross ventilation. I think it's design is better than every other bivy I have seen so far in regards of ventilation. Of course I still would expect
moisture build up over a few days, especially if buttoned up. I need the ability to set up camp in tight spots, as a climber, so this choice of system.