Reviewed in May, 2022

On the hottest nights, we chose the Seamless Burrow Bag. The synthetic insulation is minimal, but it lofts more than similar bags. Credit a combination of cylindrical and angular polyester fibers, which stack like a losing game of Tetris and thus increase airiness. One tester reported that he didn't sweat out the bag after five 45-degree nights in North Carolina's Great Smoky Mountains National Park. On a two-week road trip down the Pacific coast, another tester used the full-length, two-way zipper to ventilate and reported that the DWR treatment repelled condensation on muggy mornings. Comfort bonus: the bag's seamless construction trades baffles for internal elastic stitching that expands and contracts to match your sleeping position. The Seamless Burrow packs down to the size of a rugby ball.