The Marmot Phase 30 is easily one of the best all-around backpacking and summertime mountaineering sleeping bags and was certainly a contender for our OutdoorGearLab Editors' Choice. It was by FAR the lightest and most compressible bag in our review, performing even better than the weight focused Sea to Summit Spark III, though it's important to keep in mind the Spark III is about 10°F warmer. The only downsides of the Phase 30 are that it isn't a super warm 30°F bag and it sports some of the tightest internal dimensions in our review. However, for folks used to performance-oriented mummy-style bags, it feels similar to other mummy bags. Even our broad-shouldered testers who were used to sleeping in mummy-style bags didn't think it was much tighter than most.
Marmot Phase 30 Review
Compare prices at 4 resellers Pros: Extremely lightweight and the lowest weight model in our review, most compressible, cozy internal fabric, great hood design that is comfortable and traps heat
Cons: Not super warm for its 30°F rating, side zipper catches
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Our Analysis and Test Results
The Marmot Phase 30 is our Top Pick Award Winner for low weight and minimal packed volume. The Phase is tough to beat for those wanting a reasonably versatile bag that can embark on adventures where minimal weight and packed size are at a premium. The Phase wasn't the warmest 30° bag out there, and we felt like it was closer to a 35F rating. It was almost half a pound lighter than most of its closest competition and was the most compressible model we tested.
The Phase 30 uses 8.5 ounces of incredibly high-quality 850 fill power treated weather-resistant down. The proprietary treatment that Marmot uses id called Down Defender, and is hand-stuffed in Rohnert Park, California USA.
The 8.5 ounces is the least amount of fill weight found in any bag in our review. While it's high quality (thus having more loft and offering the best possible insulation for its weight) it wasn't as lofty as other 30°F sleeping bags in our fleet. While the Phase 30 has lots going for it, being an actual 30°F bag wasn't one of those things. It's excellent up to 40°F, though most of our testers found that we needed to layer up once we got into the 30°-35°F range.
Overall, the Phase 30 is similar in warmth to the Patagonia 850 Down 30, Sierra Designs Backcountry Bed 700, and The North Face Hyper Cat. However, we found all three of these bags were slightly warmer. The Phase was nowhere near as warm as the similarly rated (30°F) Western Mountaineering MegaLite, despite its larger dimensions, or the Nemo Salsa 30, which also features a girthier cut.
It is worth noting that the Phase 30 is warmer than we'd expect of a bag offering only 8.5 ounces of fill; this is due to the model's tight cut and exceptionally well-designed hood, which did a top-notch job at trapping the heat and was comfortable. The same could be said about the vaulted foot box that minimizes the amount of down compressed around our feet, maximizing warmth. It's not that this bag isn't warm; it's just not as toasty as most other 30F models we tested.
While it shares the same name as its colder weather sibling the Phase 20; most of the things mentioned above (about it not being warm enough for its temperature rating) don't apply. The Phase 20, despite being one of the lighter 20F bags out there and is one of the warmest in our fleet. The Phase 20 achieves this by using 14.1 ounces of high-quality down, which is more than nearly every model we tested.
At just over 1 lbs 1.5 oz (498g), the Phase 30 is one of the lightest bags for its temperature rating and is by far the lightest model in our review.
The 30 weighs less than many bags rated to 40°F or less and is one of the lightest 30F models currently available. The next closest bag was the even tighter dimensioned Sea to Summit Spark III (1 lbs 4 oz). It features mega light fabrics and only a 1/4 length zipper, though the reason it's heavier is due to the amount of insulation. The Spark III is rated to 25°F but feels at least 10°F warmer than the Phase. The Phase is an impressive 6-7 ounces lighter than other lightweight models, including our Editors' Choice, the Western Mountaineering MegaLite, (though the Megalite is roomier), and the sewn through Patagonia 850 Down 30.
The Phase achieves its low weight by using high-quality down; equipped with 8.5 ounces, along with a 10D shell fabric, this is among the thinnest material of any model we've tested. While it does feature a full-length zipper, the zipper Marmot uses is small, making it lighter and more packable, but also more prone to hanging up.
This bag's dimensions are 60" (shoulder), 59" (waist), and 45" (feet). Not exactly a "wide" bag. When compared to other performance-oriented mummy-style bags, it's not exactly narrow, either.
If you like most things about the Phase but wish it was a little roomier, we'd recommend considering our Editors' Choice Western Mountaineering MegaLite, which sports four more inches of room in the shoulders and 6.5 more ounces. What does four more inches of circumference feel like? We instantly noticed the additional space that gave us a tad more room to roll around in; it also does not feel as claustrophobic, especially if mummy bags tend to give you that impression.
We loved the incredibly silky feel of the interior fabric, which was among the very best in our review. Our review staff loved using the Phase 30 when it was hot (we felt less clammy); when it was cold out, the 30 felt cozier than the majority of models out there.
Features & Design
There aren't many "extra" features on this bag, and most of the design has been geared towards making it as light and compact as possible.
The Phase 30 uses the highest quality down, as well as the minimal amount of fill to achieve a 30F rating. It includes a top-notch hood design to increase its thermal efficiency.
There is a tiny internal zippered pocket for an alarm or a watch (if you sleep on your back), but it isn't big enough for most smartphones. Marmot uses a small gauge zipper to help save weight and lines the full-length of this zipper with a marginally stiffer fabric. They call the material "snag free" and say it helps reduce the frequency of the zipper catching on the bag's ultra-thin fabric. Unfortunately, the zipper on our model got hung up and easily snagged.
The Phase 30 is by far the most compressible model in our review. It's 25% smaller than our Editors' Choice the Western Mountaineering MegaLite or Patagonia 850 Down 30, and half the size of other models like the Nemo Salsa 30, or the Sierra Designs Backcountry Bed 700. The only contender that was comparable was the warmer Sea to Summit Spark III, which was around 10-15% larger in packed volume.
The Phase is a pretty darn versatile bag - as long as it's not too cold. The Phase, despite its low weight, features a full-length zipper that allows you to regulate heat on warmer nights.
The Phase 30 features continuous baffles that allow you to shift the down around, though we doubt many people would do this (since there's such little down to begin with). Even our most broad-shouldered reviewers found that its average dimensions (among performance mummy bags) were still plenty to accommodate wearing several layers. This bag is versatile in the sense that it works well in a reasonably wide range of conditions. It can be taken on most outings where weight and packed volume is paramount; as long as the overnight temperatures are reasonable, it also makes for a decent car camping bag.
The Phase is one of the best contenders in our review for lightweight backpacking, thru-hiking, summer-time mountaineering, or any other activity where low weight and minimal packed size will be appreciated. This bag is comfortable enough for most general purpose backpacking and camping, but other models are marginally roomier if low weight and packed size aren't big factors for you. The only thing that stops this bag from being more versatile for a wider range of activities is most people will find this bag comfortable down to 35°-40°. If the temperatures are any colder, additional layers will need to be used.
At $399, the Phase 30 is pricey, but it has higher quality down and shell materials than the other bags tested and is one of the best 30°F bags out there. Compared to other high-end bags, the Phase scores similarly and offers superior weight and decently comfortable dimensions while being close behind the Phase 30 in design and material quality. The WM Megalite is sewn and filled in California, while the Phase is filled and finished in the USA, but is primarily sewn overseas.
The Marmot Phase 30 is one of the lightest and most compressible 30F sleeping bags on the market, even if it's not quite one of the warmest. While it might not be a do-everything well model, it's a bag that excels at any activity where low weight and pack space are at a premium. If temperatures are expected to be much colder than 30 degrees, you'll need to pack extra layers or sleep in your clothes.
— Ian Nicholson