Big Agnes Zirkel SL 20

[best synthetic]

Even the highest quality synthetic-fill bags sometimes feel clammy, but not the Shoestring. “It breathes as well as my favorite down bag,” reports one tester after using it in soggy conditions in Tasmania’s Walls of Jerusalem National Park. Credit the new Pinneco Core construction, which uses a layer of breathable lamination to create a sandwich of short-staple insulation: That breathable membrane speeds moisture movement through the bag. The Shoestring is also as lofty as some down bags: Unlike most synthetics (which aren’t baffled), the Shoestring uses a “tubic” construction that forces the insulation into long, horseshoe-shaped channels. Those vertical tubes save weight, since they use trapped air to help the insulation achieve maximum loft (which boosts warmth without adding additional fill) and they continue uninterrupted over the hood.

The bag warmed our tester within moments on an icy, wet day in Colorado’s Mt. Zirkel Wilderness. “I stayed plenty cozy on that 27°F night,” she reports. The zipper doesn’t snag, thanks to a strip of stiff fabric on the draft tube that protects the coil. Bummer: The sculpted draft collar (with a U-shaped cutout that hugs the neck) is thinner and less cozy-feeling than most. “It kept out cold air as long as I didn’t move,” one tester says. And the bag is heavy and bulky: Even locked into a compression sack, the Shoestring is as big as a giant watermelon. Bonus: The various sizes accommodate a variety of body shapes: The X-Long ($240; 3 lbs. 8 oz.) fits 6’7” guys, and the women’s Betty SL ($200; 2 lbs. 14 oz.; 25°F) is cut shorter and wider at the hips. $200; 3 lbs. 10 oz.; 15°F; bigagnes.com

-Features Flow™ Construction: Insotect Flow™. A flow-optimized insulation system that delivers uniform heat distribution and natural body contouring through revolutionary vertical baffle design.
-Available in color: green
-Available in sizes: regular and long
-Hails from Big Agnes’ Divide SL Series Down line