A 2-inch-wide face muff drapes across the neck, sealing in heat. The hood cinches down to blowhole size, but the toggle is inconveniently on the outside.
The traditional mummy shape (61 inches at the shoulders tapering to 58 inches at the hip and 45 inches at the foot) offers great thermal efficiency. The broadest-shouldered hikers may feel squeezed.
Proprietary SpiraFil synthetic fill, with large, stiff, hollow fibers, lines the underside of the bag and resists compression better than the 650-fill duck down that insulates the top. This construction is best for those who don’t move much (or turn within their bags), so the SpiraFil always stays against the ground.
We felt comfortable in the mid-20s with just a baselayer, and we’d confidently take it into the upper teens with a puffy.
The 30-denier nylon on top shaves ounces, while the tough 70-denier polyester base is ideal for camping sans tent or using the bag as a lounger around camp.