Our first impression of Marmot Phase 20 was that it seemed every bit as good as the exquisite bags from Feathered Friends and Western Mountaineering. Its down is as lofty, its fabric as smooth, and it even weighs a tiny bit less. These qualities combine into a bag that's similarly cozy with a comparably excellent warmth-to-weight ratio. Hands-on testing, however, revealed a zipper that is far inferior. Its ¾-length is simply inadequate for venting excess heat on warmer nights. More importantly, the zipper's tiny size causes it to snag on the adjacent fabric without mercy. This is disappointing for a bag that costs so much and performs so well in other areas.
Marmot Phase 20 Review
Compare prices at 2 resellers Pros: Great loft, high warmth-to-weight ratio, cozy hood, convenient interior stash pocket
Cons: Expensive, frustrating zipper, narrow fit, limited ventilation options
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Our Analysis and Test Results
In our previous backpacking sleeping bag review, the Phase 20 earned a Top Pick Award for the best all around 20°F bag. With time, however, we became more and more infuriated with its small zipper. Many online customer reviews confirm this zipper is a common problem. Now, since we've gotten out hands on a couple of great Feathered Friends bags, the Phase 20 no longer takes home any OutdoorGearLab awards.
The Phase 20 is one of the warmest 3-season bags we tried. Its 14.1 ounces of lofty 850 fill power down earn it a 18.5° EN lower limit temperature rating. It also includes a hood that cinches down to a tiny, but comfortable, opening to seal heat inside. Overall, our testers thought it felt a little warmer than its EN rating.
This bag features thin 10-denier Pertex shell fabric and a tiny ¾-length zipper to minimize weight. On our scale, it weighed in at 1.74 pounds for a size long. This compares favorably with other ultra-premium bags. We believe it provides nearly the same awesome warm-to-weight performance as its Western Mountaineering and Feathered Friends competitors.
The Phase 20 features silky smooth interior fabric and lofty premium down. Together they create an incredibly comfortable interior feel. We also love this bag's hood, which unlike a lot of others, remained comfy even when cinched down fully. The narrow dimensions, however, harmed its overall score. The lower leg area, in particular, felt constrictive and so much so that we can't recommend this bag for side sleepers.
Despite its low weight, the Phase 20 didn't display an especially small packed size. Using a third-party compression sack, we measured its minimum compressed volume at 8.6 liters. This is close to the largest in the backpacking sleeping bag category. However, all the bags in this category performed reasonably well and the Phase 20 remains very small compared to most budget backpacking sleeping bags.
Like some of the other ultra-premium down bags, the Phase 20's down is contained with continuous horizontal baffles. These allow you to move feathers to the top or underside of the bag to adjust the amount of insulation. Its ¾-length zipper, however, gives you only mediocre opportunities to vent excess heat on warmer nights. Together these features counterbalance each other to give this bag moderate versatility across a range of temperatures.
Features and Design
This bag includes a convenient internal stash pocket for keeping your phone or headlamp batteries warm. As we mentioned before, we also really love its hood design and drawstring closure.
The main zipper, however, was a consistent source of frustration. To save weight, it is particularly small, but this seems to make it prone to snagging. Several online customer reviews also describe the zipper slide outright breaking or zipper snags that caused the thin fabric next to the zipper to tear. We didn't observe these problems in our tests, but they are concerns you should be aware of.
The Phase 20 is as expensive as other down bags with 850 or more fill power. For this price, you certainly get a high-quality bag that is exceptionally warm and light. The drawbacks, however, in comfort and the frustrating zipper are hard to look past. For these reasons, we believe there are several similar bags that provide a better value.
It's clear that the Marmot Phase 20 wants to compete with the best sleeping bags out there. With its 850 fill power down and feather-light fabric, it offers similar warmth and lightweight performance as the nicest Feathered Friends and Western Mountaineering bags. However, the Phase 20's uncomfortably narrow dimensions and finicky zipper ultimately spoil any serious competition. In our direct comparison tests, the Feathered Friends Hummingbird and Western Mountaineering MegaLite both proved themselves to be better designs at a similar price point.
— Jack Cramer