During a damp, tentless night in California's Mojave desert, one tester slept soundly in the Aura while his partner, in a down sack, got wet and cold. Credit the DWR treatment on the Aura's ripstop polyester shell and a silicone treatment on the fibers of the MXL PrimaLoft insulation (exclusive to REI), which also repels moisture.
The synthetic insulation blends large- and small-diameter fibers to maximize compressibility and heat retention, helping the bag stay true to its 40°F temperature rating and stuff down to the size of two Lexan water bottles. A contoured hood with cinch cords around the face and neck, along with a full-length draft tube, add warmth. The cut is narrow through the legs.