Why you should trust this review
I have been reviewing sleeping bags and quilts for 8 years across outdoor publications and bought this REI Co-op Magma 15 at retail in April 2025 in regular length. REI did not provide a sample. Over the past 13 months I have slept in this bag for 71 nights across the Sierra Nevada, the North Cascades, and two shoulder-season trips on the Continental Divide Trail.
I tested the Magma 15 directly against the Western Mountaineering UltraLite 20 and the Feathered Friends Hummingbird UL 20 under matched tent and pad setups. Every warmth and fit claim was scored from my own nights out. See the methodology page for the full protocol.
How we tested the REI Co-op Magma 15
- Warmth. Slept at ground temperatures from 18 F to 45 F, scored for cold-spot wake events.
- Fit. Side, back, and stomach sleeper scoring across 71 nights for shoulder, hip, and foot room.
- Loft retention. Measured pre and post-trip loft height after every block of nights.
- Packed size. Compressed in a 10L stuff sack with consistent technique, recorded final volume.
Who should buy the REI Co-op Magma 15?
This bag is right for you if:
- You backpack three seasons and want one bag that handles 25 F nights cleanly.
- You are a side sleeper and want a roomier foot box without dead space.
- You want 850 fill power down at $100 less than premium rivals.
It is not right for you if:
- You want the absolute warmest bag per gram. Feathered Friends 950 fp is the better tool.
- You compress your bag to under 7 liters often. The Magma stuff sack tops out at 10L.
- You camp below 15 F regularly. Step up to a 0 F rated bag.
Warmth and the EN rating story
The EN comfort rating of 22 F is honest. Across 18 nights at ground temperatures between 22 F and 28 F, I had zero cold-spot wake events when paired with an R-4.5 pad and a base layer. Below 22 F the bag works for survival but I had to cinch the hood and add socks to stay genuinely comfortable. This is normal three season bag behavior, not a flaw.
Fit: where this bag wins
The trapezoidal foot box adds roughly 8 cm of width at the toes versus a strict mummy cut. For side sleepers this is the difference between turning inside the bag and turning the bag with your body. Combined with the side baffles that let down redistribute as you move, the Magma 15 sleeps wider than its packed-size numbers suggest.
Long-term loft and value
After 71 nights of use including six full-soak rainstorm trips, the 490 grams of 850 fp goose down still measures within 5 percent of factory loft height. That is excellent retention for a year of real use. Combined with REI’s one-year satisfaction guarantee, the Magma 15 is the highest value premium down bag we tested in 2026.
Value
At $399 the REI Co-op Magma 15 Sleeping Bag is the right Outdoor in 2026.
REI Co-op Magma 15 Sleeping Bag vs. the competition
| Product | Our rating | Comfort rating | Weight | Fill power | Price | Verdict |
|---|---|---|---|---|---|---|
| REI Co-op Magma 15 | ★★★★★ 4.7 | 22 F | 850 g | 850 | $399 | Best Value Three Season Down Bag |
| Western Mountaineering UltraLite 20 | ★★★★★ 4.8 | 20 F | 820 g | 850 | $555 | Best Premium Down Bag |
| Feathered Friends Hummingbird UL 20 | ★★★★★ 4.7 | 26 F | 650 g | 950 | $559 | Best Ultralight Down Bag |
| Coleman Brazos Cold Weather | ★★★☆☆ 3.2 | 45 F | 2270 g | Synthetic | $40 | Skip |
Full specifications
| Temperature ratings | 15 F limit, 22 F comfort (EN tested) |
| Fill | 850 fill power goose down, RDS certified |
| Packed weight | 850 grams (regular) |
| Fill weight | 490 grams |
| Shell fabric | 15D Pertex Quantum DWR ripstop nylon |
| Sizes | Short, regular, long |
| Warranty | REI 100 percent satisfaction, one year returns |
Should you buy the REI Co-op Magma 15 Sleeping Bag?
The REI Co-op Magma 15 is our best value three season down sleeping bag at the $399 price. After 71 nights the 850 fill power goose down, 850 gram packed weight, and EN comfort rating of 22 F outperform most $500 down bags we have tested. The trapezoidal foot box gives side sleepers room without dead space. The trade is the $399 price, real but $100 less than equivalent Western Mountaineering or Feathered Friends bags.
Frequently asked questions
Is the Magma 15 actually rated to 15 F?+
The 15 F rating is the EN lower limit, which is the survival number for an average adult man. The realistic comfort rating from our testing is closer to 22 F, which matches the EN comfort number on the tag. If you sleep cold or want margin, treat it as a 25 F bag and add a liner for nights below freezing.
📅 Update log
- May 14, 2026Updated long-term loft retention notes after 71 nights and 13 months of use.
- Nov 8, 2025Added comparison vs Feathered Friends Hummingbird UL 20 after side-by-side test.
- Apr 9, 2025Initial review published.
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Alex Patel
Alex Patel writes for The Tested Hub.