Gear Review: Big Agnes Bellyache Mountain SL 17/Lithia Spring SL 15

“I had some of my best nights of sleep ever in cold, rainy conditions in this bag,” says a tester of this lofty, 700-fill DownTek bag. Credit the Bellyache’s generous upper body cut, for one—restless sleepers and big guys could move freely inside the bag. (The Bellyache is the only bag here that comes in an extra long option, which measures 65 inches at the shoulder and 57 at the hip.)

The quick-lofting insulation (equal on top and bottom, unlike some Big Agnes models, which lack insulation on the bottom and are designed to be paired with a sleeping pad) also garnered praise. “It’s a fluffmonster,” says a Utah tester. Deluxe features add to the cush factor: A soft, U-shaped draft collar (the only one of its kind in this test) sealed in warmth, and an exceptionally effective hood cinched so well, a tester slept without her usual fleece beanie on a cold night in Utah’s Gravel Canyon.

The bag proved toasty down to its rating for testers over 5’8”, but shorter, skinny testers found the bag too voluminous—and therefore, chilly—in the 30s. It also scored high on breathability in a wide range of conditions: “This bag epitomizes warm and dry—I never had to unzip,” says a tester who slept fully battened down on a 35°F night in Oregon’s Roaring River Wilderness. A two-way zipper allows for foot venting or even unzipping most of the bag to use as a blanket, as one tester did on a 60°F night in Colorado’s Dominguez Canyon Wilderness. Ding: It’s bulky when packed (though not quite as large as the Kelty). $300 (women’s Lithia Springs is $350); 2 lbs. 8 oz.; 17°F/15°F; bigagnes.com

Overall: 4.1

Warmth to weight: 4.2

Comfort: 4.7

Packability: 3.6

Water resistance: 4.3

Tester Notes

Laura Katers: This bag has phenomenal loft. Insulation wraps around you, with equal insulation on the top and bottom. This was so comfortable I found this bag harder to crawl out of perhaps more than any other bag, ever. The zipper occasionally snagged on me, which was a tad annoying.

Elisabeth Kwak-Hefferan: Warm and toasty, and I love the drapey draft collar. I didn’t even have to zip the bag up the whole way to stay warm with that cozy thing around my neck. And it’s cozy but not constricting—I could move around inside the bag, a big plus.

Dan Larson: This is a big, comfortable bag for thrashing around in! Awesome fabric feel and great loft. It’s a little loose and big for me to heat up quickly (I’m 5’7”). I didn’t like the warmth-to-bulk ratio. This is the only bag that made me add a layer to stay warm during the night.

Becca Stubbs: I usually sleep cold, but this bag helped me overcome a deep chill after stargazing too long into the desert sky. My icicle feet warmed up quickly without ever getting sticky or sweaty. No hot water bottle needed! A rare experience for me. Hands-down one of the better bags I’ve seen breathability-wise. Not an ultralight, or ultra-compressible, but an ultra-comfortable.