Everything To Know About NEMO Soul Endless Promise Synthetic Mummy Sleeping Bag
Our pick for best-in-class sustainability as of Q1, 2025
The new-for-2025 NEMO Soul Sleeping Bag (Endless Promise Synthetic Mummy) is our pick for most sustainable option on the market thanks to the unique combination of recycled materials and end-of-life recyclability! What’s more, it exhibits overall great stats for a synthetic bag, and has nearly all of the right features and performance attributes for a very reasonable price. That being said, performance optimizers will still prefer ultralight down quilts, which can weigh as little as half as much for a similar temperature rating.
The following stats reflect the 30F regular length version
- Weight: 31.0 oz
- Price: $270
- Down: Zerofiber™ 800 postconsumer recycled synthetic insulation
- Fabric: 100% recycled polyester taffeta
- Peers: NEMO Coda, NEMO Pulse, NEMO Disco, NEMO Forte, NEMO Riff
- Top Competitors: Marmot Trestles Elite ECO, Enlightened Equipment Revelation APEX
- Pros: Best-in-class sustainability. Lightweight. Good warmth-to-weight. Great feature set, particularly ventilation. Affordable.
- Cons: Lower warmth-to-weight and bulkier-when-packed than down. Sleeping bags are inferior to quilts.
Compare to more great options in our guide to the best sleeping bags and best backpacking quilts.
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NEMO Soul Construction, Materials, Sustainability, Fit
Material sustainability is what sets the NEMO Soul apart from popular competitors in its peer group, like the Marmot Trestles Elite Eco. While both Trestles and Soul are made with 100% recycled fabrics and 100% recycled insulation, Soul’s monopolymer composition allows for it to be recycled at end-of-life, where as Trestles goes straight into the landfill.
NEMO claims that the 100% postconsumer recycled Zerofiber 800 insulation is “aerospace grade” and the “highest-performing synthetic fill possible – ultralight, water-resistant, and warm when wet.” While the latter two are definitely true as performance characteristics of all synthetic insulations, this bag is textbook light-not-ultralight, and there is no information provided to back up the claim that it’s the highest-performing synthetic fill or what exactly makes it aerospace-grade. While that could be marketing jargon, our initial hands experience does indicate that it’s a high quality synthetic fill competitive with other top options currently available on the marketplace.
No denier information is provided about the 100% recycled shell and liner fabrics, but we’d ballpark this polyester taffeta at 20d.
Soul gets a classic mummy shape, and isn’t particularly generous, nor is it particularly tight. Rather, exactly what you expect when you think mummy sleeping bag. If you’re in between two sizes, we recommend sizing up.
NEMO Soul Physical Features
Key Physical Features of the NEMO Soul
- Draft Collar
- Footbox Vent
- Thermo Gill Chest vent
- Half-Zip Entry
- Genderless
Draft Collar
NEMO Soul has a massive, 5″ tall draft collar tracing the entire perimeter of the neck area, top and bottom side. It’s very, very effective at draft prevention.
Footbox Vent
The footbox vent is another luxury feature that runs a zipper across the diameter of the footbox. Open it up on warm nights, close it when cold. In general, we prefer cinches to zippers here (or no vent at all) to save weight. But it’s not a big deal either way.
Chest Vent Gill
The Thermo Gill Chest Vent is an 18″ zipper that runs along the torso paralleling the entry/exist zipper. Open it up for a 2″ wide vent that parts the insulation. However, the vent is purposefully blocked by a thin layer of breathable fabric, which regulates how much heat/moisture can escape. This allows for fine tuning, while a majority of ventilation can be handled by the double separating main zip on the other side.
Double Separating Half-Zip Entry
NEMO Soul’s half-length entry zipper is a great design choice for a sleeping bag intended to minimize weight, and we fully endorse the decision to not go full length. But it does come at cost – firstly, it’s harder to enter/exist, but that is a trivial issue. More importantly, you can’t fully unzip it for maximum air flow, though the foot box vent and Thermo Gill help to compensate for this.
Genderless
Given that gender is a social construct applied to human beings, what does it even mean for a sleeping bag to be genderless? We suppose it has to do with temperature ratings, of which it gets two; one based on lower limit (traditionally the men’s rating), and one based on the comfort limit (traditionally the women’s rating). Perhaps what they’re getting at is that Soul is listed with both ratings upfront, instead of one primary and one secondary. We also note that it doesn’t have widening at the hips, so it certainly isn’t a women’s cut. All in all, this classification is a bit of a mystery.
Who Should Choose It, Who Shouldn’t?
Who should choose it
- Those seeking the most sustainable option
- Value shoppers
- People who frequently hike in damp climates
- People who will commit to actually sending it back to NEMO for recycling once they’re done using it.
Who should NOT choose it
- Ultralight enthusiasts wanting the best performance possible, they should choose a down quilt
- People who regularly hike in dry climates, since you won’t actualize the moisture resistant benefits of synthetic insulation
NEMO Soul Review Conclusion
Due to its recycled materials and recyclability, NEMO Soul Sleeping Bag is the most sustainable model in its category, and a competitive option at a competitive price in the overall synthetic insulation genre. However, down is still more effective than synthetics, and quilts are more effective than sleeping bags, making it above-average-but-not-exciting from a pure performance perspective. Nonetheless, we love what NEMO is doing on the eco-friendliness front, and hope to see their Endless Promise program continue to thrive.
