REI Co-Op Magma 15
Summary
Price At Time Of Writing | $399.00
Our Overall Rating | 86 out of 100
Pros - Warm, well-built and available in a wide range of sizes
Cons - Slightly heavier than ultralight alternatives, may be too warm for summer
Verdict - Great comfort and value for cold-weather backpackers
Technical Specifications
Packed Size - 16.5x7.8in
Weight - 2lb 3.6oz
Fill - 850-Fill Goose Down
Our Analysis & Ratings
The REI Co-op Magma 15 is a feature-rich, high-performance sleeping bag that punches above its weight for cold-weather backpackers. Although it's labelled as a 15-degree bag, the warmth it delivers edges closer to a true 10-degree performer, thanks to an impressive 23.3 oz of 850-fill-power water-resistant down in the medium size. Designed with comfort, fit and sustainability in mind, the Magma 15 is an appealing choice for three-season use, especially for those who want quality, warmth and inclusive sizing without the ultra-high price tag.
Comfort - The plush 15-denier nylon lining feels soft against the skin, while the contoured mummy shape allows for a snug yet non-restrictive experience, even for side sleepers. The sleeping bag includes a generously sized trapezoidal footbox, a well-fitted hood and an insulated neck yoke that eliminates cold drafts. Side sleepers, cold sleepers and those who shift positions frequently will appreciate how the bag moves with them instead of bunching. The draft collar and hood cinch down smoothly to seal in warmth, while the interior stash pocket offers convenient storage for a phone or headlamp.
Construction - REI built the Magma 15 with a focus on thermal efficiency and thoughtful details. Variable baffle spacing helps maintain consistent down distribution, reducing cold spots. The hood and insulated yoke design combine for excellent heat retention at the head and shoulders. The shell is made from 15D recycled nylon with a non-fluorinated DWR treatment to fend off light moisture and condensation. A well-designed zipper system wraps around the chest for ease of use and features a snag-resistant strip and draft tube to prevent heat loss. Finally, all stitching and materials feel durable yet lightweight, indicating quality construction without added bulk.
Features - The Magma 15 is packed with functional features that cater to real-world needs. The most notable is its inclusive size range: nine options that vary by length and width, allowing nearly anyone to find a tailored fit. The contoured hood, anti-snag zipper and internal stash pocket all add utility without complication. An insulated yoke replaces a traditional sewn-in draft collar, comfortably filling the gap at the neck to lock in warmth. The bag includes a compression sack for backpacking and a mesh storage sack for loft preservation at home.
Size/Weight - Depending on the size selected, the Magma 15 weighs between 2lbs and 2lbs 11.3oz. For a sleeping bag that performs reliably in sub-freezing temperatures, these are very respectable numbers. The medium size clocks in at 2 lbs 3.6 oz, which is heavier than some ultralight competitors but warmer and more forgiving in terms of comfort. Compressed volume ranges from 6 to 9.4 liters, fitting easily into a 45–50-liter pack. The generous down fill also makes it more substantial than a minimalist summer bag, but it still packs down surprisingly small for its warmth class.
Versatility - While it’s marketed as a 15-degree bag, its actual performance makes it better suited for temperatures around 10–20 degrees Fahrenheit. That makes it great for spring and fall trips, high-altitude treks, or any colder environment where ultralight bags might fall short. This does, however, make it too warm for hot summer nights unless partially unzipped. The wide sizing range also makes it versatile for a range of body types, sleeping styles and backpacking goals. That said, the heavier weight might be overkill for fastpackers or summer-only adventurers.
Overall - The Rei Co-Op Magma 15 delivers reliable warmth, premium features and excellent fit options at a competitive price. It may not be the lightest on the market, but the added warmth and comfort are well worth the tradeoff for most three-season backpackers.
