A 550-fill down mummy bag rated to 20°F, sold by Kelty as the Cosmic Down 20. People pick it because it is one of the least expensive real down bags, and it packs smaller than most synthetic bags at the same price.
Specs
- Weight: Short 2 lb 3 oz; Regular 2 lb 7 oz; Long 2 lb 11 oz (maker and REI)
- Temperature: 20°F rating; ISO comfort 31°F, ISO lower limit 21°F (REI)
- Fill: 550-fill-power down; fill weight 14.6 / 16.4 / 18.8 oz (Short / Regular / Long)
- Fits up to: 66 / 72 / 78 in
- Shoulder girth: 58 / 62 / 64 in; hip girth 56 / 58 / 60 in
- Shell: recycled 50-denier polyester taffeta with PFC-free DWR; lining recycled 20-denier nylon taffeta (REI)
- Features: trapezoidal baffles, full draft tube and collar, two-way anti-snag zipper, internal stash pocket, roomy footbox
- Stuff sack: 8 x 13 in, 10.7 L (Regular); included
- REI rating (men's): 3.8 of 5 from 49 reviews (as of 2026-10-19)
What reviewers say
Treeline Review calls it the best value camping bag it has tested, with features you usually see on bags that cost far more, and notes that down keeps its loft for many years longer than synthetic fill. CleverHiker agrees on value and likes the snag-resistant zipper, hood and stash pocket. Both point out it is heavier and bulkier than premium down bags. They differ on fit: CleverHiker found the mummy cut narrow, while Treeline found it roomier than expected. Keep in mind the ISO comfort rating is 31°F, so most people will want to treat it as a 30-degree bag for comfortable sleep.
Good
- Real down at a budget price
- Packs smaller than similar-price synthetic bags
- Good features: draft collar, two-way zipper, stash pocket
- Down lasts for years with care
Not so good
- Heavier and bulkier than premium down bags
- Comfort rating (31°F) is well above the 20°F name
- Mummy fit can feel narrow to some sleepers
- 550-fill down loses loft if it gets soaked
Who it's for
New backpackers, car campers and families buying several bags who want down without the high price. Ounce-counting backpackers and cold sleepers headed below freezing should look at a warmer or lighter bag.
Sources
Last checked 2026-10-19. Specs from the maker; review notes summarized in our own words.