Reasonablle quality bivy for reasonable price - Sierra Designs Backcountry Bivy Sleeping Bag

This bivy is of medium construction quality (ripstop nylon) but seems to be able to serve as a good fall/winter bivy. The packaging says "waterproof" but it does not seem to be completely waterproof, but rather more like water-resistant. I have not had a chance to fully test it in the rain, as I just received it in early December. I tried it outside last night in 32' and it kept me warm enough (along with a 10'F sleeping bag, plus liner, plus good sleeping pad). The key for warmth is a good sleeping pad. A big plus with this bivy is ample room inside to move around (I purchased the "long" size). Also, it is lightweight, breathable, and has a large U-shaped opening. A suggestion for improvement would be to make it from Gore-Tex, but the cost would inevitably increase. I purchased this bivy for about $100 (on sale), so if you don't want to break the bank, this bivy might be for you.