This is one awesome bivy! After bringing the Advanced Bivy along for multiple week-long excursions in Blue Ridge, I have come to rely on this guy. When the temps are warm, the bivy breathes nicely and keeps the bugs at bay. In cold weather it's a cozy non-restrictive safe haven from biting winds. It is absolutely waterproof, ridiculously lightweight, and packs down to nothing. If you're considering purchasing a bivy, give the OR Advanced the attention it deserves.