High Peak USA Chameleon 20/0

In the quest for maximum warmth at minimum weight, we have a new standard setter.

Brand: High Peak USA

Model: Chameleon 20/0

First, bag-swapping testers were suspicious (“No way that’s warm enough—you take it”) and then greedy (“Never mind, I’ll pack the Plasma again today”). Who wouldn’t want to carry so little and sleep so warm? Whether in Alaska, the Adirondacks, or Capitol Reef, the response was unanimous: The cloudlike Plasma kept even cold-sleeping editors toasty on chilly nights that flirted with the bag’s temp rating (in both the 15°F and 30°F versions). The trick? Every detail is focused on efficiency.

The Insotect FlowGate system contours to your body, offering even insulation so none of the bag’s 900-fill down is wasted. Vertical baffles conceal smaller chambers spaced 10 to 15 inches apart; these cells help reduce cold spots by isolating the down and keeping it from shifting. And a 10-denier Pertex shell is 25 percent lighter than comparable shells; it’s so thin sunlight shines through, but we dragged the Plasma across slickrock like a toddler’s blankie with nary a lost feather.

And the shell enhances ultrafast drying: Four days of damp Denali trekking eventually soaked the footbox, but it dried with body heat after a few hours. A fat draft tube, snug collar, and deep, contoured hood seal the deal. Fit is narrow and efficiently trim, but not claustrophobic. (The zipper, however, required a little trial and error for a snag-free close.) Magic every morning: The 15 compresses down to volleyball size. Plasma 15: $469; 1 lb. 12 oz. (reg.); Plasma 30: $419; 1 lb. 6 oz. (reg.); two lengths; marmot.com

When you don’t know what Mother Nature has in store on your next camping trip, you can be prepared with the Chameleon Sleeping Bags that are perfectly suited for changing temperatures. The main feature of the Chameleon bag is the detachable cover that can add extra insulation for a colder night. When temps rise, you can simply zip off the top layer and have a bag that is just right. The Chameleon bag also features a full-length draft tune and collar, a drawstring hood and Invista Thermolite Quallo insulation for maximum warmth. The shell is made of ripstop nylon and the liner is made with polyester taffeta. The two-way zipper can also be zipped together with another bag.

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