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Big Agnes
Bellyache Mountain SL Sleeping Bag: 17F Down

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A traditional mummy bag upgraded with the power of water-repellent down.

Twelve years ago Big Agnes dove headfirst into the fray of designing gear for the outdoor world. It introduced the unique Big Agnes System (sleeping bags with a pad sleeve on the bottom instead of insulation) and defined a new level of comfort for hitting the sack at night. Now, for the first time since the brand was born, Big Agnes  has revived the traditional mummy bag design and redesigned its insulation and technology from top to bottom. The result is Bellyache Mountain SL17-Degree Sleeping Bag, a technical, three-season sleeping bag that conquers wet nights in the spring and cold mornings in the fall.

Perhaps the most notable feature of the Bellyache is the Downtek Insulation. This water-repellent down retains loft, breathability, and insulation value even if the down itself gets wet from rain or moisture. This gives you a serious advantage over traditional down insulation that clumps and lies flat at the first sign of moisture. Even with high-end insulation, a sleeping bag is only as good as the baffles that hold its insulation and the Bellyache uses Flow Construction, one of the most innovative baffle constructions in the industry. Insotect Flow uses a series of vertical baffles with internal gates that eliminate vertical and lateral clumping by constantly evening the distribution of insulation from head-to-toe, thus eliminating cold spots. Along with draft-stopping features like a seal around the neck opening, a wedge between the sleeping bag and sleeping pad connection, and a no-draft tube along the zipper, this sleeping bag offers reliable, regular warmth throughout the night.

Amazingly, for all its cold-and-wet-weather advantages, this sleeping bag maintains a weight well under three pounds. Along with your insulating layer and a wool hat, this versatile 17-degree bag should be an essential part of your kit whether you're pitching a tarp in the Pacific Northwest or pitching a single-wall in the Carolinas.


  • Cozy 17F-degree temperature rating keeps you toasty-warm early spring through late fall
  • Light and lofty 700-fill DownTek water-repellent down insulation won't clump up or freeze, because it won't get wet
  • Traditional mummy shape gives body-contouring, efficient warmth with some wiggle room
  • Durable nylon fabric shell resists water, and smooth nylon taffeta lining resists stains
  • Draft collar, draft wedge, and draft zipper ensure warm air stays in and cold air keeps out
  • Left- and right-zip bags mate together for a cozy coupling
  • Insotect Flow construction evenly distributes heat with flow-optimization and baffle design
  • Mesh storage sack and nylon stuff sack included for convenient storing and packing
  • Item #BAG2995
[shell] nylon, [lining] nylon taffeta
700-fill DownTek water repellent down
Draft Collar
Max User Height
[regular] 6 ft, [long] 6 ft 6 in
Shoulder Circumference
[regular] 60 in, [long] 62 in
Hip Circumference
[regular] 54 in, [long] 56 in
Foot Circumference
[regular] 36 in, [long] 38 in
Stuff Size
17.5 x 8 in
Stuff Sack
yes, nylon
Storage Sack
yes, mesh
Fill Weight
[regular] 21 oz, [long] 23 oz
17 F
European Norm Comfort Rating
28 F
European Norm Lower Limit Rating
17 F
Claimed Weight
[regular] 2 lb 7 oz, [long] 2 lb 10 oz
Recommended Use
camping, backpacking
Manufacturer Warranty

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