Tell you what, I used the MSS (modular sleep system) for a few years when I was in the Army, in the snow and in the desert. Personally, I'd spend the bucks on a nice, lightweight, easily packable bag rather than this. It's too bulky, loses loft too easily, and is not particularly warm. The bivy is nice, and it works rather well to keep the rain out, if you can find just the bivy I'd go for it. Otherwise I'd invest in a decent bag, not this.