SectionHiker.com Backpacking Gear Reviews and FAQs 
The REI Magma 15 is an ultralight sleeping bag for three-season use. Weighing just 1 lb 12.2 oz, it’s insulated with 850 fill power goose down with an outstanding warmth-to-weight ratio. Its variable-sized baffle construction, a draft collar, zipper draft tube, and trapezoidal footbox are all high-end features commonly found on premium sleeping bags costing much more.
REI Magma 15 Down Sleeping Bag
Warmth
Weight
Comfort
Features
Versatility
Specs at a Glance
- Gender: Men’s (a women’s specific version is also available)
- Size: Regular
- Weight: 1 lb 12.22 oz
- Down Fill Weight: 15.9 oz
- Insulation: 850+ fill power goose down
- Draft collar: Yes
- Draft tube: Yes
- Anti-snag Zipper: Yes
- Water-Resistant Down: Yes
- Fabric: exterior – Pertex Quantum; lining – 15 denier nylon ripstop
- Shoulder/hip: 63”/57”
- Length – Regular: 6’0” (72”)
- Zipper: full length; left-hand
- Stuff Sack Size/Volume: 7.5 x 15 inches/10.9 liters
- Compressed size – Regular: 5.2 Liters
- ISO Temperature Ratings:
- Comfort: 28F / -2C
- Lower Limit: 16F / -9C
The REI Magma 15 is a three-season sleeping suitable for use in spring, summer, and autumn although it may be too warm for use (without serious venting) in high summer, depending on your location and whether you’re a warm or cold sleeper. Its sweet spot is definitely in the cooler months during autumn and spring, when the days are shorter, the nights are cooler, and you need to a sleeping bag that will keep you warm as your metabolism slows during the longer nights.
The Magma 15 has what REI calls a curvy silhouette shape, that’s designed to save weight by eliminating the extra fabric and insulation that boxier sleeping bags require. While it is “fitted”, the Magma 15’s interior is not cramped and there’s still plenty of room inside regardless if you’re a back or side sleeper. The bag is however strongly shaped with a curved side-to-chest zipper and variable-sized baffles that help keep minimize the number and size of the air spaces in the bag that your body has to heat before you can get warm.
Anti-Snag Zipper
The zipper on the Magma 15 is well designed and does not snag because it has a tightly woven barrier that keeps the down baffles away from obstructing the zipper’s path. The zipper extends from the bottom of the footbox and then angles up from about mid-chest, over the left shoulder to the neck/collar closure. It has a robust pull loop and the teeth are encased in a hard plastic shell that slides easily for entry/exit or venting.
Interior
The inside of the Magma 15 is soft to the touch and constructed with a plush 15-denier nylon ripstop. The baffles are variably spaced throughout the interior of the bag to maintain a high loft and minimize cold spots throughout the interior. The construction is not sewn through but uses a boxed style baffle adapted to work with the Magma 15’s unique shape.
Hood and Yoke
I usually wear a hat in a sleeping bag to ensure that my head stays warm even if I toss and turn at night. I found that I didn’t need a hat when using the Magma hood because it was so warm and well-fitting. The hood also followed me easily as I turned at night, rather than fighting against me as some mummy bags do. The hood is large enough to fit a pillow, which I find to be a must-have during the long cold nights of autumn and early spring.
The Magma 15 also has an insulated “yoke” that augments what is typically a fixed draft collar around the neck portion of a sleeping bag. It’s a baffle of down that lays on over your neck and upper chest to prevent warm air from leaking out of the bag when you move around at night, called the “bellows effect.” NEMO has a similar feature on all of their sleeping bags. They’re equivalent to draft collars but are slightly larger and easier to use without any additional adjustments.
Comparable sleeping bags
When you compare the REI Magma 15 against other premium mummy sleeping bags, it is quite attractive option in terms of overall weight, insulation weight, and feature set.
| Make / Model | Price | Down Fill Power | Total Weight | Down Fill Weight |
|---|---|---|---|---|
| REI Magma 15 | $369 | 850 | 28.2 oz | 15.9 oz |
| Feathered Friends Lark 10 UL | $579 | 950 | 31.3 oz | 20 oz |
| Marmot Helium 15 | $400 | 800 | 33 oz | 19.8 oz |
| NEMO Kayu 15 | $390 | 800 | 30 oz | 15 oz |
| REI Igneo 17 | $299 | 700 | 31 oz | 16 oz |
| Therm-a-Rest Hyperion 20 | $410 | 900 | 20 oz | 13 oz |
| Western Mountaineering Badger15 | $605 | 850 | 40 oz | 23 oz |
| Western Mountaineering Apache 15 | $540 | 850 | 33 oz | 19 oz |
Recommendation
The REI Magma 15 sleeping bag is a lightweight and relatively affordable option for those seeking to expand their backpacking adventures well into spring and autumn. It is well constructed, weather-resistant, and comfortable when the nights are cold and long. Weighing just 1 lb 12.2 oz, the Magma 15 provides superior warmth when temps get down into the 20’s and high teens while having little additional impact on the overall size or weight of your backpacking kit. We’re impressed!
Disclosure: REI donated a sleeping bag for this review.
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Does is use RDS down?
Yes it does.
A friend of mine bought this bag for a Sept. Bonds traverse. He was cold with temps in the 30’s and he’s not a cold sleeper. I was warm in my Feathered Friends Flicker 30.
Nice bag, detailed review, as usual. REI always gives you your money’s worth and then some.
For the past 7 years I’ve had an overstuffed WM Megalite good to 20 F. and been very happy with it in the “shoulder seasons” and even summers her in the mountain west.
I just bought a women’s magma 15 a few weeks ago (I’m a guy), and had a pretty warm and cozy sleep in it at about 22F nightly temps. In fact, I think I’m the only one out of a group of 4 that slept comfortably.
I can’t fathom how that other guy slept cold. This bag is a furnace.
I wonder why the women’s bag is heavier and more expensive? A long women’s ( 72 inches) is 2 pounds 6 ounces and $389.
The men’s regular ( 72 inches) is 1 pound 12 ounces and $369 .
and though it says the women’s is roomier in the hip–both are measured at 60 inches. The men’s has 3 extra inches in the shoulders.
There are 8 more ounces of down in the womens than the mens. I don’t know any of the science here but i think the reasoning is something along the lines of; women sleep colder than men therefore require more insulation. Don’t know how true that is but it is common for womens bags to weigh more. I’m guessing that is why J.D. above got the womens version, to get some extra fill/warmth.
The science is that women sleep about 10 degrees colder than men because they have less body mass.
Women’s bags are comfort rated at 15d, hence we more down.
That bag is a 28degree bag, women’s REI, by comfort rating and reflective by more down used. The 15d comfort rating reflects keeping you alive not comfortable. Women’s bags tend to have a comfort rating reflective of actual bag rating vs men’s that usually are 10-15d less than advertised.
To note, a real 15d bag like FF has about 4oz more.
Even the marmot 15 has more down, and I believe is comfort rated at 20d.
Hip and chest measurements different.
Philip,
What are your thoughts/experience with compression sacks for sleeping bags?
I have the previous version Magma 10, and it’s 850 down compresses very well. But I am worried about damaging the down and reducing the loft.
Just unpack it when you store it at home. It will be fine. Down springs back well after being compressed. Don’t worry about it.
I have used the men’s long 15 degree version of this bag for three years now (I am 6’3”, 190 lbs.). I backpack out west and in the summer with mild temps at moderate altitude, it works great as a quilt. On trips over 10,000 feet with it fully zipped up, I have been cold a number of times in a tent using the Neoair Xtherm pad which provides a lot of insulation. I am a side sleeper which makes staying warm more of a challenge. In addition to being cold, I find the shape of the bag very restrictive for side sleeping. To me, the diagonal zipper is a bit awkward. I was pretty surprised when I saw above how much less down this bag has vs. the women’s version. Almost 9 oz. for an equivalent size! Overall, I do not like the shape of this sleeping bag and I believe that a 15 degree bag should have more down fill. I am going to try the WM Alpenlite with overfill. I tried this bag out for comfort in the store and it did not seem restrictive at all. Hoping it will be warmer.
The women’s version has more down in it because women need more insulation than men.
I have this bag womens long version I got at REI garage sale (had a tiny hole I repaired) I have never even had to zip it up. I just throw it over me as a quilt, open with my feet in the box, and am warm. I have had it down into low 20s and in a snow storm. I am normally a cold sleeper. I bought a second one already for family to use.
It is a remarkably good value. Glad it’s worked out for you!
The women’s Magma is a good value relative to the men’s. The women’s large has 1 lb. 8.5 ounces of fill while the men’s large has only 1 lb 1.3 ounces of fill. 1 lb. 8.5 ounces of fill is a ton of fill for a 15 degree bag. Both the men’s and the women’s cost the same amount – $399. The women’s sleeping bag is a good value while the men’s sure does not seem to be at the same price. Not sure why both sleeping bags cost the same amount even though the women’s bag has almost 30% more down.
The Women’s Long is the same price as the Regular and will fit a person up to 72″ height. Their website says it has decreased shoulder room and increased hip room but shoulder girth is only 3″ less than the Men’s and the hip girth appears to be the same. The shoulder girth is actually more than what I have in my usual sleeping bag, however I don’t need another bag. I have five down sleeping bags and last I checked, I’m only able to use one at a time.