Can a -20°F bag really be both light and roomy? Yes, says a broad-shouldered tester who slept comfortably in this wider-than-average mummy at -15°F in Colorado’s Mt. Zirkel Wilderness. One trick? Loft where you need it, none where you don’t. That’s the Big Agnes strategy, which saves weight by eliminating insulation on the underside of the bag. Bottom warmth comes from your pad, so bring a good one in winter (or two; our tester was on an insulated air mattress and a closed-cell foam pad). Other tricks? Ounce-saving 800-fill down and a thin-but-water-resistant Pertex Quantum shell. With these, Big Agnes designers increased the bag’s dimensions (shoulder girth is 67.5 inches for the regular) and still kept overall weight and bulk remarkably low for such a warm bag.
Insulation is enhanced by Insotect Flow construction, which features vertical baffles that improve heat distribution and mesh partitions that keep down from shifting, preventing cold spots. Convenience and comfort features include a stuffable pillow pocket sewn inside the hood (rare in this category), a wedge of insulation that seals in heat where the bag meets your pad, and a no-snag zipper backed by a fat draft tube. The built-in pad sleeve fits most mats.