It used to be that sleeping bags' degree ratings were determined in various ways, so conventional wisdom dictated that you buy a bag with a temperature rating at least 10 to 15 degrees lower than the lowest temperature you'd expect to be camping in. That's starting to change. For 2010, most manufacturers have (finally) implemented the third-party European Norm test, which uses a sensor-equipped mannequin inside a controlled chamber to assign ratings based on the temperature at which an average 25-year-old woman can sleep comfortably throughout the night (Comfort), the same threshold for an average 25-year-old man (Limit), and the temp at which a 25-year-old woman can survive the night (Extreme). You can see the resultsmany bags' labels now denote all three temperatures. The upshot: A bag may now be significantly more insulated at the same temperature rating than it was last year. Try the bags on in the storelighter bags sometimes mean narrower cuts, which can be claustrophobic.
This year's winner is the 15-degree bag from Montbell. "Not just different. Better" is how one tester sums it up. The Ultra Light Super Spiral's major tech innovationspiraled bafflesmade it the most comfortable and best-functioning bag we tested this year. Far from a gimmick, the spiral baffles drape more evenly over the body, creating a closer fit. And because the seams are sewn with elastic thread, the bag literally hugs the luxurious, top-shelf 800-fill down insulation to your body at rest, and expands by up to 20 percent when you move around. We could actually sit up and cross our legs inside ita boon for restless sleepers. Another benefit of the diagonal construction is that the baffles are longer, meaning fewer seams to let heat out. All this in a tiny package: The gossamer-light 12-denier fabric and high-grade down make for a bag that packs to the size of a bread loaf.
2.3 lbs; montbell.us
Compressibility: 4.6 (out of 5)