Therm-a-Rest Hyperion 20°F

Cut weight and stay warm with this featherweight bag.


Weight 1 lb, 4 oz


If you’re ruthless about cutting weight, you’ll like the Hyperion. It’s one of the lightest models in this temp category, thanks to a narrow, heat-saving shape (shoulder circumference is 57 inches), a half-length zipper, and 900-fill goose down. It packs down to the size of a honeydew and kept us warm on an 18°F night in the Pyrenees. Even the price—well below the competition—is ruthless.

Features-wise, the Hyperion has enough to keep sleepers happy. Its hydrophobic down stayed lofty on a rainy night in Wyoming when one editor’s tent failed, and the hood snugs tight with a single cinch. The 10-denier nylon lining isn’t luxurious, but it’s definitely soft enough.

Side sleepers take note: The bag puts most of the down on top; if you roll and pull the bag with you, you’ll feel the cold sneak in. The zipper also snags and its half length isn’t ideal for warmer nights. “But that’s common in this category and a small price to pay for a bag I can fit in my cookpot,” one ultralighter says.