REI Magma 15 Sleeping Bag Review – Your Ultimate Cold-Weather Companion?

Discover the REI Magma 15, a lightweight, warm, and highly durable sleeping bag ideal for three-season backpacking and camping adventures.
REI Magma 15

REI Magma 15

Explore the Performance and Comfort of the REI Magma 15 in Challenging Outdoor Conditions
The REI Magma 15 is a lightweight, warm, and comfortable sleeping bag, ideal for three-season use, offering excellent value with its high-quality materials and thoughtful design.


Warmth & Insulation
Packability & Weight
Comfort & Fit
Durability & Materials
Versatility & Features


  • Lightweight and Compact
  • Warmth and Insulation
  • Breathable and Comfortable
  • Durable Construction
  • Practical Features


  • Price
  • Limited Size Options
  • Not Fully Waterproof
  • Down Insulation Vulnerable to Wet Conditions


Brief Overview

The REI Magma 15 is a high-performance sleeping bag designed to keep you warm and comfortable in a variety of outdoor conditions. With a temperature rating of 15°F (-9°C), this sleeping bag is intended for three-season use, making it an excellent choice for backpackers and campers who venture into cooler climates. The Magma 15 boasts a combination of high-quality materials and advanced design features that cater to serious outdoor enthusiasts.

Initial Impressions and Context of Testing

Upon unboxing the REI Magma 15, the first thing that strikes you is its lightweight and compact nature. Weighing in at just over 1.75 pounds, it’s immediately apparent that this sleeping bag is designed with backpacking in mind. The outer shell is made of a durable yet soft nylon fabric, and the overall construction feels robust and well-made.

For testing, I took the Magma 15 on a week-long backpacking trip in the Rocky Mountains, where temperatures varied from mild during the day to freezing at night. The varied conditions provided an ideal testing ground to evaluate the bag’s performance, particularly its warmth, comfort, and durability. My initial impressions were promising, and I was eager to see how it would perform in the field.

Technical Specifications

Key Features and Technology

The REI Magma 15 sleeping bag is packed with advanced features and technologies designed to enhance its performance in the field. Here are some of the standout aspects:

  • Temperature Rating: 15°F (-9°C), making it suitable for three-season use.
  • Insulation: The bag is filled with 850-fill-power goose down, providing exceptional warmth-to-weight ratio and compressibility.
  • DownTek Treatment: The down insulation is treated with DownTek, a water-repellent finish that helps the down maintain loft and insulation properties even in damp conditions.

Design and Materials

The design and materials of the REI Magma 15 reflect a focus on durability, comfort, and functionality:

  • Shell and Lining: Made from lightweight, durable 15-denier Pertex® Quantum nylon, which offers a soft feel and high tear strength.
  • Baffle Construction: The bag features a contoured hood, trapezoidal foot box, and a full-length zipper with an insulated draft tube to prevent cold spots.
  • Zippers: Equipped with anti-snag YKK® zippers for smooth operation and longevity.

Dimensions and Weight

  • Regular Size: Fits users up to 6 feet tall with a shoulder girth of 60 inches and a hip girth of 57 inches.
  • Long Size: Fits users up to 6 feet 6 inches tall with a shoulder girth of 62 inches and a hip girth of 59 inches.
  • Packed Size: Compresses down to approximately 7.5 x 15 inches, making it easy to pack into a backpack.
  • Weight: The regular size weighs 1 lb. 12 oz., while the long size weighs 1 lb. 15 oz.

Additional Features

  • Hood: The contoured hood cinches tightly around your head to minimize heat loss.
  • Draft Collar: Prevents heat from escaping and cold air from entering.
  • Interior Pocket: Convenient for storing small items like a phone or headlamp.
  • Compression Sack: Comes with a stuff sack for easy packing and a storage sack for long-term storage.

These technical specifications highlight the REI Magma 15’s commitment to quality and performance, making it a reliable choice for backpackers and campers seeking a high-quality sleeping bag for a variety of conditions.

Performance Evaluation

Fabric Performance

  • Breathability: The REI Magma 15 excels in breathability, thanks to the 15-denier Pertex® Quantum nylon shell. This fabric is designed to allow moisture to escape while keeping warmth in, which is crucial for maintaining comfort throughout the night. During my backpacking trip, I found that the bag effectively managed internal moisture, preventing the clammy feeling that can occur in less breathable bags.
  • Waterproofing: While not fully waterproof, the Magma 15 features a durable water repellent (DWR) finish on the outer shell that helps shed light rain and dew. This feature is particularly useful in damp environments, where condensation inside a tent or unexpected moisture can otherwise compromise down insulation.
  • Durability: The Pertex® Quantum nylon shell and high-quality stitching contribute to the bag’s overall durability. After several nights of use, including rough handling during packing and unpacking, the fabric showed no signs of wear or tear.

Weather Resistance

The REI Magma 15 is designed to handle a variety of weather conditions. Its 850-fill-power goose down insulation provides excellent warmth, even in temperatures as low as 15°F (-9°C). I tested the bag in temperatures ranging from just above freezing to the mid-20s Fahrenheit and found it consistently warm. The DownTek-treated down retains its loft and insulating properties even in slightly damp conditions, which is a significant advantage over untreated down.

Practical Features

  • Hood: The contoured hood is designed to cinch tightly around your head, minimizing heat loss and maximizing warmth. The hood’s ergonomic design allows for easy adjustment, even when wearing gloves.
  • Draft Collar and Draft Tube: The insulated draft collar and draft tube along the zipper are key features that prevent cold air from seeping in and warm air from escaping. These additions significantly enhance the bag’s overall thermal efficiency.
  • Interior Pocket: The small interior pocket is perfect for keeping essentials like a headlamp, phone, or glasses within easy reach. This feature adds a layer of convenience, especially when you need to access items quickly during the night.
  • Compression Sack and Storage Bag: The included compression sack allows the bag to be packed down to a manageable size, making it easy to fit into a backpack. The storage sack is useful for long-term storage, ensuring the down maintains its loft and longevity.

The REI Magma 15’s performance in fabric breathability, water resistance, and practical features make it a standout choice for backpackers seeking reliability and comfort in a lightweight package.

Fit and Comfort

Sizing and Fit

The REI Magma 15 is available in two sizes: Regular and Long, designed to accommodate different body types and heights. The Regular size fits users up to 6 feet tall, while the Long size is suitable for users up to 6 feet 6 inches tall. The shoulder girth of 60 inches (Regular) and 62 inches (Long) provides ample room for movement without feeling constricted. The hip girth of 57 inches (Regular) and 59 inches (Long) ensures that even broader bodies can find a comfortable fit.

During my testing, I found the sizing to be true to REI’s specifications. The sleeping bag fits snugly without being too tight, allowing for some movement without compromising warmth. This balance is crucial for those who might feel claustrophobic in tighter bags but still want the thermal efficiency of a well-fitted bag.

Comfort During Various Activities

  • Sleeping Positions: The REI Magma 15 is designed to accommodate a variety of sleeping positions. Whether you are a side sleeper, back sleeper, or stomach sleeper, the bag provides enough space to shift comfortably throughout the night. The trapezoidal foot box is a notable feature that allows for natural foot positioning, preventing the cramped feeling often experienced in tighter sleeping bags.
  • Hood and Draft Collar: The contoured hood and draft collar add significant comfort by maintaining warmth around the head and neck. The hood’s adjustable drawcord lets you customize the fit, ensuring that you stay warm without feeling restricted. The draft collar prevents cold air from entering and warm air from escaping, enhancing overall comfort during colder nights.
  • Fabric Feel: The inner lining of the Magma 15 is made from a soft, 15-denier Pertex® Quantum nylon, which feels pleasant against the skin. This fabric not only contributes to the bag’s lightweight nature but also enhances the overall sleeping experience by preventing any scratchy or uncomfortable sensations.
  • Temperature Regulation: One of the standout comfort features of the Magma 15 is its ability to regulate temperature effectively. The 850-fill-power goose down insulation, combined with the breathable nylon shell, ensures that you stay warm without overheating. This balance is particularly important during fluctuating nighttime temperatures, where too much insulation can lead to discomfort.


The REI Magma 15 excels in providing a comfortable sleeping experience, catering to various body types and sleeping positions. Its thoughtful design features, such as the contoured hood, draft collar, and trapezoidal foot box, contribute to a cozy and warm night’s sleep. Whether you are a restless sleeper or someone who prefers a snug fit, the Magma 15 offers the right blend of space and insulation to ensure comfort throughout your outdoor adventures.

Pros and Cons


  • Lightweight and Compact: Weighing just over 1.75 pounds, the REI Magma 15 is exceptionally lightweight, making it ideal for backpackers who prioritize reducing pack weight. It compresses down to a small size, easily fitting into any backpack.
  • Warmth and Insulation: The 850-fill-power goose down provides excellent warmth, even in temperatures as low as 15°F (-9°C). The DownTek treatment ensures the down stays dry longer and retains its loft in damp conditions.
  • Breathable and Comfortable: The 15-denier Pertex® Quantum nylon shell is breathable, allowing moisture to escape and maintaining comfort throughout the night. The inner lining is soft against the skin, enhancing the overall sleeping experience.
  • Durable Construction: High-quality materials and robust stitching ensure the Magma 15 is durable and long-lasting, capable of withstanding the rigors of regular use.
  • Practical Features: The contoured hood, draft collar, and trapezoidal foot box add significant comfort and warmth. The interior pocket provides convenient storage for small items, and the anti-snag YKK® zippers ensure smooth operation.


  • Price: The REI Magma 15 is relatively expensive, which may be a deterrent for budget-conscious backpackers. However, the high-quality materials and performance justify the investment for serious outdoor enthusiasts.
  • Limited Size Options: While the bag comes in Regular and Long sizes, the shoulder and hip girth might not accommodate all body types, particularly those with broader shoulders or hips.
  • Not Fully Waterproof: Although the DWR finish provides some water resistance, the Magma 15 is not fully waterproof. In very wet conditions, additional waterproofing measures (like a bivy sack) may be necessary to keep the sleeping bag dry.
  • Down Insulation: While down insulation is excellent for warmth and compressibility, it can lose its insulating properties when wet. Despite the DownTek treatment, synthetic insulation might be preferable for extremely damp or wet environments.


The REI Magma 15 offers a range of benefits, including lightweight construction, superior warmth, and excellent comfort features, making it a top choice for backpackers and campers. However, its higher price and limited waterproofing are factors to consider when making a purchase decision. Overall, the pros significantly outweigh the cons, especially for those seeking a reliable and high-performing sleeping bag for their outdoor adventures.

Comparative Analysis

When comparing the REI Magma 15 to the Feathered Friends Swallow UL 20 and the Nemo Disco 15, several distinctions emerge that highlight the strengths and weaknesses of each sleeping bag.

REI Magma 15 vs. Feathered Friends Swallow UL 20

The REI Magma 15 and the Feathered Friends Swallow UL 20 are both high-quality, down-filled sleeping bags designed for three-season use. The Magma 15, rated for 15°F, offers a slightly warmer experience compared to the Swallow UL 20, which is rated for 20°F. Both bags use high-fill-power down (850 for the Magma and 900 for the Swallow), ensuring excellent warmth-to-weight ratios. However, the Swallow UL 20 has an edge in terms of weight, being marginally lighter due to its premium 900-fill down. The Swallow UL 20 also tends to be more expensive, reflecting its use of higher-grade materials. In terms of fit, the Magma 15’s spacious design is beneficial for those who prefer a bit more room, whereas the Swallow UL 20 is designed for a snugger fit, which some might find restrictive but enhances thermal efficiency.

REI Magma 15 vs. Nemo Disco 15

Comparing the REI Magma 15 to the Nemo Disco 15 reveals differences in design philosophy. The Nemo Disco 15 is designed with side sleepers in mind, featuring a spoon shape that provides more room at the elbows and knees. This makes the Disco 15 particularly comfortable for those who move around a lot in their sleep. The REI Magma 15, on the other hand, follows a more traditional mummy shape, which is optimized for thermal efficiency and packability. In terms of insulation, both bags use high-quality down, but the Magma 15’s 850-fill down offers a slightly better warmth-to-weight ratio than the Disco 15’s 650-fill down. However, the Disco 15 includes additional features like the Thermo Gills, which allow users to vent excess heat without letting cold drafts in, adding versatility in varying temperatures. Price-wise, the Magma 15 tends to be more affordable, making it a strong contender for budget-conscious hikers seeking high performance.

In summary, the REI Magma 15 excels in warmth, weight, and affordability when compared to the Feathered Friends Swallow UL 20 and the Nemo Disco 15. However, for those who prioritize a lighter pack weight or unique features catering to specific sleeping styles, the Feathered Friends and Nemo options might be worth the extra investment.


The REI Magma 15 is a standout sleeping bag that balances warmth, weight, and comfort, making it an excellent choice for three-season backpacking and camping. Its 850-fill-power goose down insulation provides exceptional warmth even in temperatures down to 15°F (-9°C), while the DownTek treatment ensures the down remains effective in damp conditions. The Magma 15’s lightweight and compact design make it ideal for backpackers who need to minimize pack weight without sacrificing comfort. Despite its higher price, the investment is justified by the high-quality materials and thoughtful design features, such as the contoured hood, draft collar, and practical interior pocket. While not fully waterproof, its water-resistant finish adds a layer of protection against light moisture. Overall, the REI Magma 15 offers excellent value for money, particularly for those seeking a reliable, high-performance sleeping bag for a variety of outdoor adventures.

Further reading