BD winter bivy
The weight and compression are great. I used it in heavy rain, it helps about as much as it weighs zero. Not that it is designed for that anyway. Otherwise it does a fantastic job of blocking morning dew and snow wont stick to it either. Its excellent when used with a shelter, I'm able to use my down bag more often thanks to this! The tiny zipper is a pain with cold/wet hands, and the material has a "static cling" effect when damp. Great for the minimalists! BD has great customer service too.