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 frustrated with its small zipper. Many online customer reviews confirm this zipper is a common problem. Now, with the inclusion of a couple of great Feathered Friends bags, the Phase 20 no longer takes home any OutdoorGearLab awards.
Performance Comparison
The Phase 20 is an awesome bag that suffers from unfortunate zipper issues. Had we not added Feathered Friends bags to our review, it likely would have won a Top Pick Award.
Warmth
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 but slightly colder than the Feathered Friends Swallow.
Weight
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.
Seen from overhead it's easy to spot the strong taper from the head to the foot of the bag. Several testers thought the footbox felt uncomfortably narrow.
Comfort
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 enough 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.
The Phase 20 came with one of the lightest stuff sacks, but the same sack was ineffective at compressing the bag to anywhere near its minimum volume. We recommend getting an after-market compression sack.
Packed Size
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.
Moving down around inside the Phase 20 is as easy as sliding your arm against the bag on a flat surface. Here the author moves feathers from the top to the underside of the bag in anticipation of warmer outside temperatures.
Versatility
Like some of the other ultra-premium down bags, the Phase 20's down is contained with continuous horizontal baffles. This allows 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.
We really like the zippered stash pocket inside the Phase 20, but it was too small for a tester's iPhone 6.
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.
There is so much to love about the Phase 20, but definitely not the zipper. Here it's seen snagged on the lofty draft tube--an all too common occurrence.
Best Applications
With its superior warmth, this bag is best suited for colder 3-season applications. Specifically, we think it's ideal for the backpacking in average spring or fall temperatures and summer at higher elevations. Its awesome warmth-to-weight ratio is also great for mountaineering or alpine hiking and rock climbing.
Value
The Phase 20 is as expensive as the 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 better value.
Conclusion
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 weight 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 Merlin and Western Mountaineering MegaLite both proved themselves to be more capable but at a similar price point.
