When weight and space really count, the MSR AC Bivy is the best and most efficient way to get the all-condition protection you need. Maximum waterproof-breathable fabric coverage delivers the best possible breathability, while an extra-tough floor with our finest, 10,000mm DuraShield coating lets you rest confidently through anything. A zippered shoulder entry with mesh allows excellent bug-free ventilation and makes it easy to get into and use while sitting up.