Gear Review: Big Agnes Tumble Mountain 3-Season Sleeping Bag

An innovative down bag with no cold spots

Roomy and Warm

“I felt like I was crawling into my own bed when I slipped into this bag,” said our tester after a week in the Smokies. “It’s big enough to change socks or layer-down in the middle of the night.” Which is likely: The Tumble Mountain uses a proprietary technology that lets designers construct a plus-size bag without sacrificing thermal efficiency. The 725-fill down is stuffed into long vertical baffles. Typically, that type of construction would result in shifting down and cold spots. But new “FlowGates”, made from twisted baffle netting that locks the down in place, allow designers to precisely control loft.

It also means fewer stitchlines and “fill spots” (which keeps construction costs down). The half-length integrated pad sleeve means that your upper-body relies on the mattress for bottom-side insulation, but your legs are enveloped in down and free to move, a plus for thrashers and people with cold feet (you can use a full- or three-quarter-length pad). Testers stayed warm down to 10°F. A polyester shell repelled heavy condensation and moisture that splashed in under a tarp. The in-hood pillow pocket is one of the best we’ve tested; stuff it with a fleece and your cushion never moves.

Green bonus: There’s recycled material in the shell, liner, drawcords, and zipper. $290; 2 lbs. 13 oz.; 20°F