Mountain Equipment Xeros 7-degree F down sleeping bag: Among the best in its class

Posted on: December 20, 2017

MSRP: $500

Selecting the right sleeping bag for the conditions can make the difference between a miserable night or a restful one. Pick a bag that's too warm and you're likely to end up stuck in a sweat sack, with the material stuck to your body so tight you'll wake up feeling as if you're being swallowed by a giant snake in the jungle. Go with a bag that's too light and you're likely to chatter through frozen misery like Sam McGee. As with most alpine gear, it's nice to have a quiver of sleeping bags, but it's even better if you have a particular one that works well in most conditions.


Mountain Equipment's Xeros 800-fill, Russian Goose Down bag has become my go-to since I got it last February: I have never experienced a more efficient sleeping bag. I've used it in warm, sweaty conditions as well as cold, wet conditions, and the bag has kept me remarkably dry and comfortably warm the whole time. It is also the lightest bag I've ever used.

At 38 ounces (2.38 pounds), with a temperature rating of 7F, a comfort rating of 23F and an "extreme risk rating" of -23F, the Xeros is competitive with zero-degree sleeping bags as well as with 20-degree sleeping bags made by other major brands. The colder-rated bags have more insulation and therefore are heavier, with a typical weight hovering around 3.5 pounds or more. On the other end of the spectrum, some of the high-end 20-degree bags range from about 1.5 to 3 pounds. With its 7-degree rating, the warmth-to-weight ratio of the Xeros places it among the best products of its class.

The author enjoys the comfort of the Mountain Equipment Xeros 800-fill, Russian Goose Down sleeping bag inside his bivy sack on the second morning of his solo ascent of Prodigal Sun (V 5.7 C2, 900') in Zion National Park, October 22. [Photo] Derek FranzThe author enjoys the comfort of the Mountain Equipment Xeros 800-fill, Russian Goose Down sleeping bag inside his bivy sack on the second morning of his solo ascent of Prodigal Sun (V 5.7 C2, 900') in Zion National Park, October 22. [Photo] Derek Franz

A big reason why the Xeros has kept me so comfortable in such a wide spread of temperatures, from about 60F to 20F, is because of its ability to vent excess body heat and repel moisture. The DriLite Loft Xero 10D outer shell is described by Mountain Equipment's website as "ultra-light, highly breathable and water-resistant." I would say the material has lived up to this description. I used the bag for a bachelor party in Utah's San Rafael Swell in late May. I was sure I was going to be too hot but wanted to try it out. Although the nights were certainly warm, I slept well and was surprised at how the material wicked away my sweat. I could tell that the bag had absorbed a lot of the perspiration, but my skin was remarkably dry and the down was still lofty. Of course, I'm sure that if I spend too many warm, sweaty nights in the bag, it will degrade the down much faster than if I use the bag strictly for its intended conditions. But it's good to know the bag can vent so well.

At best, a sweaty bag is uncomfortable; at worst, the sweat can result in freezing as the moisture compromises the insulation, and before long, your wet body becomes a popsicle.

Along that same principle of keeping insulation dry, it's obviously important to keep rain, snow and condensation out. My Xeros bag was put to the test when a fast-moving storm caught me in a portaledge without a rainfly in Zion National Park in late October. Fortunately, I had a bivy sack that helped provide some immediate protection, but the portaledge collected the heavy rain and quickly turned into a stock pond. I braced myself for a wet and cold night, certain I would wake up soaked to the skin and be forced to retreat in the morning. But the Xeros stayed dry and warm, which was good because the second night on the north-facing wall was even colder, dipping down to about 30F. I had some of the best sleep in months even though the insulated water dromedary hanging next to me froze partway through. I also slept great through two cold, snowy nights in Indian Creek last February—on that trip I was actually a little too warm in the back of my truck with the Xeros.

Mountain Equipment designed the Xeros with trapezoid baffles that are designed to minimize dead-air space and maximize loft. Elasticated stitching is incorporated into the seams of these baffles as well so that the bag gently hugs your entire body, further minimizing extra space within the cavity of the bag. But doesn't dead-air space provide insulation, a buffer zone? Yes and no—a small amount helps insulate, but too much empty air will merely be more space your body has to keep warm. I used to prefer long sleeping bags that gave me more space to move around or stash extra clothes, but then I realized my feet stayed warmer when I didn't have an extra 10 inches of room at the bottom. If staying as warm as possible is the priority, getting a bag that fits you is important.

Like all cold-weather bags, the Xeros has a hood and neck collar with elastic drawstrings to seal out the drafts. One aspect that is different from other designs is a magnetic plastic button for closing the draft collar. The button is not a snap: it slides into its connecter from the side and the magnet holds it in place. Releasing it requires sliding the button out of its slot instead of pulling it apart. On several occasions, I woke up to find the button had closed itself and my reaction was to try pulling it apart, which didn't work and led to some brief, mild panic. A self-closing button like this can be great for staying warm but also could be annoying if you are claustrophobic.

This bag is light, warm and competitively priced for its class—not the cheapest and not the most expensive. It would be hard to find a better value.

Enjoying the only hour of direct sun in two days on Prodigal Sun. [Photo] Derek FranzEnjoying the only hour of direct sun in two days on Prodigal Sun. [Photo] Derek Franz

Alpinist Digital Editor Derek Franz's first real sleeping bag was an Army Surplus mummy bag that was heavy and smelly but plenty warm for his needs when he started backpacking in Rocky Mountain National Park at age 7 with his dad.

Lightweight (1075 grams/38 ounces, or about 2.38 pounds)
Warm (rated to -14C/7 F)
Vents excess body heat and moisture well and is water resistant
Quality goose down and trapezoid baffle design maximize loft and minimize dead-air space
Competitively priced for its quality

Magnetic closure on the draft collar might annoy some people


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