First bought this bag in an effort to put together an ultralight setup. First trip out, took this bag with me on a weekender up to King's Canyon. Lows at night were in the 40s and I was perfectly comfortable. My old summer bag is a +20 and a full 2 pounds heavier than the Hydrogen. For camping in the Sierra in the summer a +30 is normally just fine. My only addition to this bag was to use a compression sack with it. (A granite gear xs works great) Takes up less room in my pack than my rain gear now. I've seen some comments about the half zipper, but it really didn't bother me at all.