Sea to Summit Alpine II (with Ultra-Dry Down

[hybrid]

Love the water resistance of synthetic insulation but want the packability of feathers? The hybrid Flash offers both: It pairs 800-fill goose down on top (where the plumes can loft fully) with PrimaLoft Sport underneath (where resilient synthetic fibers resist ground moisture and feel cushy even when compressed beneath body weight). Waterproof/breathable nylon on the hood, sides, and footbox gives the bag outstanding water resistance: On one soggy October hike in Washington’s North Cascades, condensation-soaked tent walls didn’t dampen the fabric or insulation. The zipper is among the best we’ve seen. “It never snags, not even with a fast, one-handed pull,” reports our tester, who also issues props for the unusually wide storm flap and fat draft tube that thwart any hint of a breeze through the zipper coils.

With a shoulder girth of 60 inches, the mummy cut is efficient but unrestrictive for all but the biggest hikers. Separate cinch cords for the hood and collar allow for precise adjustments. Thanks to its down content, the Flash packs smaller (the size of a jumbo coffee can) than comparably rated all-synthetic bags. But side-sleeping testers found that exposing the bottom of the bag resulted in cool spots. And the women’s version (which is three ounces heavier, thanks to additional insulation) is noticeably warmer than the men’s: Our male tester (a self-professed “hot sleeper”) was chilly in the mid-30s, but the ladies’ version kept our gal “toasty warm” in comparable conditions. $259; 1 lb. 9 oz.; 32°F; rei.comThe best alpine cocoon for ski touring, mountaineering and climbing.

Features: Contoured mummy, 3D NanoShell™, Ultra-Dry Down™, differential cut shell with 3D side walls, offset baffles, 60/40 fill ratio, side block baffle, anatomically tapered foot box, zip draft tube with anti-snag, neck draft tube with dual elastic adjustment, cushioned internal hood drawcord with dual adjustment, 2 way YKK #5 side zip, medium sized internal zip pocket. Includes lightweight Ultra-Sil® compression bag, mesh storage cell and laundry bag.