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Photo: REI

The REI Co-op Magma 30 Sleeping Bag is a comfortable and warm mummy-style bag ideal for three-season use in much of the Lower 48. The Magma 30 utilizes 15D Pertex Quantum fabrics, 850 fill power water-resistant down, an anti-snag zipper, an insulated yoke, and a trapezoidal footbox.

Weighing in at 20 oz (567 g) and priced at $319.00, this bag provides value for backpackers looking to acquire a lightweight sleeping bag without breaking the bank.

Features and Specifications


Specifications (size regular*)

  • Claimed weight: 20 oz  (567 g)
  • Measured weight: 20.67 oz (586 g)
  • Temperature rating: 30 F (-1 C)
  • Fill type: 850-fill-power goose down, with hydrophobic treatment
  • Fill weight:  8.5 oz (241 g)
  • Dimensions: 80 in x 27 in (fits 72 in long sleeper) (203 cm x 69 cm)
  • Compressed dimensions: 6 in x 13 in (15 cm x 33 cm)
  • Shell fabric: 15d ripstop nylon (Pertex Quantum)
  • Lining fabric: 15d ripstop nylon
  • Shoulders:  63 in (160 cm)
  • Hips: 57 in (145 cm)

*Available in long length

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The REI Magma 30 in the Bitterroot National Forest, Montana.

I’ve spent hundreds of nights in lightweight sleeping bags in the 15 F to 30 F (-9 C to -1 C) range, from the Appalachians to the Cascades. The Marmot Plasma 30, Feathered Friends Hummingbird UL20, and Marmot Pinnacle 15 are the bags I’ve used the most. Depending on conditions, I use a short Therm-A-Rest NeoAir XLite or a regular Therm-A-Rest NeoAir AllSeason for my sleeping pad. I often pair these with a short Therm-A-Rest ZLite or RidgeRest for puncture protection and additional insulation. During the shoulder seasons, I wear thicker base layers (200 weight) and a down jacket when temperatures are forecast to drop below the rating of the sleeping bag I’m using.

I prefer down bags because of their weight-to-warmth ratio and their longevity. As a backpacker with an athletic build, I don’t need much extra room in my bags.  But I do toss and turn some and appreciate not feeling like I’m in a straitjacket. I also appreciate the extra space when drying out damp clothes, warming up clothing items before putting them on in the morning, or keeping a water filter from freezing.

For the past two years, a Feathered Friends Hummingbird UL20 has been my most-used sleeping bag for trips from June to September in Montana, Idaho, and Washington. It is rated for 20 F and features a much slimmer cut than the REI Co-op Magma 30 Sleeping Bag.

Description of Field Testing

IMG 0621
Airing the REI Magma 30 out and allowing some damp spots from tent condensation to dry before packing up camp.

I tested the REI Co-op Magma 30 Sleeping Bag on several backpacking trips in August and September in Wyoming and Montana. The coldest temperature was 26 F (-3 C) and the warmest 44 F. I encountered no significant amounts of precipitation or high relative humidity when testing this sleeping bag. I tested this sleeping bag inside of a Six Moon Designs Lunar Solo shelter, an MSR Hubba tent, and in the back of my vehicle at trailheads.

Performance Assessment

I assessed this bag by noting how its design and features performed when used during overnight trips. I visually inspected the Magma 30 with an eye towards performance and construction quality before use and after the testing period concluded. My performance assessment addresses:

  • Cut
  • Insulated yoke
  • Fabric
  • Manufacturing quality
  • Baffles
  • Storage
  • Warmth


It is almost an understatement to call the Magma 30 “roomy,” despite it being a mummy-style bag. It features one of the amplest cuts of any mummy bag I’ve experienced. It was easy to change socks without stressing the fabric, something that has not been the case with other sleeping bags I’ve used. The cut also allowed plenty of room for me to dry slightly damp clothes during the night and warm clothes before putting them on in the morning.

There was also plenty of room in the trapezoidal footbox. The trapezoidal shape allows for the natural splay and positioning of feet when back sleeping. There was adequate room in the footbox to store my water filter at night to keep it from freezing. Despite having such a roomy cut, this bag did not seem to suffer from any notable cold spots.

Insulated yoke

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The REI Magma 30’s hood and insulated yoke.

Most of the sleeping bags I’ve used either employ a dedicated draft collar with a cinch cord or an overstuffed baffle (i.e., a passive collar) in the shoulder area. Both have positives and negatives. Draft collars can feel somewhat strangling at times and add another set of cords to have to adjust when entering and exiting the bag. Passive collars can often be less effective than desired when pushing the limits of a bag. The insulated yoke on the REI Co-op Magma 30 blends the best of both. There are no additional cords to fiddle with. Instead, there is a tube of down-filled fabric that drapes across your collarbone and prevents heat from escaping the bag and cold drafts from entering.


Although I never used this bag without a shelter, I employed it on several nights in windy conditions (10 to 15 mph steady wind, gusts 25 to 30 mph). At the time, I was also testing the Six Moon Designs Lunar Solo, a shelter with mesh ventilation panels through which the wind easily entered. I found the Pertex Quantum fabric blocked wind adequately to prevent any heat loss and that no cold chills penetrated the seams.

The Lunar Solo’s single-wall design gathered condensation overnight. The Magma’s fabric resisted this moisture (for the most part) when brushing up against the shelter’s wall. It became slightly damp on relatively humid and still mornings from this contact, but never seemed to wet out. I noticed no impact on the bag’s loft in these conditions.

Less than a half-hour in the sun seemed to dry the fabric completely. The 15 denier nylon was comfortable against the skin when it was warm enough to forego baselayers. It did not feel clammy, even early in the night, when temperatures were only in the low 50s.

Manufacturing quality

I encountered no noticeable issues with the quality of this bag’s components or assembly. I noticed no down leakage during my testing. The zipper, zipper pulls, fabric, and cords are durable and well-balanced between lightweight and sturdy. The main zipper pull has an easy to grab plastic pull attached with a thin cord via a girth hitch on the outside. The inside has a 2.5 in (6 cm) piece of webbing to use when zipping or unzipping from inside the bag.

IMG 0669
Zipper close-up; another zipper at the bottom allows for venting at the footbox.

The primary zipper is covered with a plastic piece that separates the teeth from the fabric, and the result is smooth zipping. During my testing, I did not experience any snagging at all.

An additional zipper pull at the footbox allows for ventilation.


This bag utilizes traditional horizontal baffles of variable sizes to maximize warmth and keep the down located where it is needed. Near the chest and torso, the baffles are approximately 5 in (13 cm) wide and progressively widen to around 7 in (18 cm) at the footbox. Baffle loft was consistent throughout at approximately 3.25 in (8 cm).

In my experience, this resulted in no cold spots during the night despite the roomy cut.


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REI Magma 30 in the included stuff sack; one-liter Nalgene bottle for scale.

The REI Magma 30 comes with a small stuff sack for backpacking as well as a mesh storage sack for long-term storage. The included stuff sack is slightly too small to make for easy stuffing. The sack is water-resistant, but not waterproof. When compressed in the included stuff sack, the Magma 30’s dimensions are approximately 6 in x 13 in (15 x 33 cm).

For these reasons, I opted to use a Sea to Summit eVent Compression Dry Sack during my testing. Several of the trails I hiked included river fords, and I wanted to ensure my sleeping bag stayed dry in case I took an unexpected swim.


I found the Magma 30 was true to its temperature rating – when used with lightweight base layers, head covering, socks, and a full-length sleeping pad with an R-value greater than 2.5.

I wore midweight base layers when pushing this bag below its limit and found it to be comfortable. When using a three-quarter length sleeping pad with my backpack under my feet, I was – as expected – not quite as warm at similar temperatures as when using a full-length pad. If you typically use a three-quarter length pad, you will likely find yourself limited to within a few degrees of the Magma 30’s comfort rating of 39 F (4 C).

Overall, I found this bag to be adequate to the lower limit of 30 deg F (-1 deg C) for backpackers who sleep on the warmer side and use a full-length sleeping pad.

Product Strengths and Limitations


  • This zipper is one of the best I’ve used on a sleeping bag – the design was snag free during my testing.
  • Hydrophobic down provides peace-of-mind in extended damp conditions.
  • Fabric is comfortable against the skin and sheds moisture effectively .
  • Cut is roomy without cold spots.
  • Insulated yoke is effective at preventing heat loss, but not as cumbersome as a full-wrap draft collar.
  • Good value.


  • Provided stuff sack is too small and offers minimal water resistance.
  • Rating is optimistic for cold sleepers unless paired with a full-length pad with R-value of 3 or higher.

Compared To…

The REI Co-op Magma 30 Sleeping Bag compares favorably to other sleeping bags in the 30 F (-1 C) category and is the most competitively priced. Despite having a lower fill weight than other bags in this category, the Magma 30 still performed well at the lower limits of its temperature rating. This performance is the result of features (such as the insulated yoke and variable baffles) that focus on thermal efficiency without added weight.

ProductREI Co-op Magma 30Feathered Friends Hummingbird UL 30NEMO Kayu 30Big Agnes Flume UL 30
Weight20 oz (567 g)21.3 oz (606 g)26 oz (737 g)22 oz (624 g)
Temperature Rating30 deg F (-1 C)30 deg F (-1 C)31 deg F (-1 C)30 deg F (-1 C)
Fill Power850950+800850
Fill Weight8.5 oz (241 g)11.5 oz (327 g)11 oz (312 g)12 oz (340 g)
Baffle OrientationHorizontalHorizontalVerticalVertical, horizontal in footbox
Hydrophobic TreatmentYes (unspecified treatment method)NoNikwaxDownTek
Footbox DescriptionTrapezoidalTrapezoidalShaped to maximize thermal efficiency, waterproof and breathable fabric to protect against tent condensationErgonomic
Liner and Shell Fabric15d ripstop nylon and Pertex Quantum 15d ripstop nylonFlite 15d ripstop nylon and Pertex Endurance UL30d nylon taffeta and 20d ripstop nylon30d nylon taffeta and 20d ripstop nylon
Special FeaturesInsulated yoke, footbox zipperNoneThermo Gills allow venting to regulate temperature without draftsInsotect Flow in baffles to distribute heat


This sleeping bag performed as expected based on the temperature ratings provided by the manufacturer. Despite having considerably less down fill than some other bags in this category, it was still true to its rating when used in lightweight base layers and with midweight socks.

When midweight base layers were used, and the bag was on a pad with 4.0 R-Value, this bag was comfortable several degrees below its rating. The features and fabrics used in this bag are well-designed (the zipper and insulated draft yoke in particular), high-quality, and result in a sleeping bag that meets expectations and provides excellent value. The Magma 30 will suit the needs of many backpackers in summer or three-season conditions (depending on the region).

Review Rating: Recommended

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For backpackers looking for an affordable lightweight sleeping bag that doesn’t skimp on features and delivers on its temperature rating, the REI Co-op Magma 30 Sleeping Bag is an appealing choice. With quality components and user-friendly features, this sleeping bag – boasting the best warmth-to-weight ratio of the bags made by REI – is less expensive than other comparable bags without cutting corners.

While not attempting to offer a radically innovative product or compete down to the last gram in the ultralight market, REI has begun offering high-performing pieces of gear. Many of these products are ideal for those looking to save weight on major items such as tents and sleeping bags while staying within a modest budget. This sleeping bag is an example of their success in this endeavor. I recommend it without hesitation.

Where to Buy

  • Buy the REI Co-op Magma 30 Sleeping Bag here.

Related Content

  • REI also offers the Magma Trail Quilt 30 for those who prefer a quilt rather than a traditional sleeping bag. See our review here. 

Product Review Disclosure

Updated October 18, 2019

  • Product(s) discussed in this review were either acquired by the author from a retailer or otherwise provided by the manufacturer at a discount/donation with no obligation to provide media coverage or a product review.
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