We know down bags have the best warmth-to-weight ratio in their category, and the same goes for sleeping pads with feathers. The 700-fill goose feathers inside this mat provide an R-value of 7 (many four-season pads top out at 4) and give it the best warmth-to-weight/bulk ratio of any pad we’ve tried. “We slept with only a tarp in 20°F temps with light snow in Arizona’s Blue Range, and I was warm every night of our 10-day trip,” says our cold-sleeping tester. The 3.5-inch-thick mat compresses to about the size of a 1-liter bottle, thanks to the mummy profile that tapers from 20.5 inches to an unusually narrow 13 inches at the feet. Bummer: not much rolling around space. Consider the 5-inch-wider version if you want elbowroom. Bonus: The pad is tough, thanks to the laminated shell treatment (most pads are simply coated). We spent two weeks in the high desert with no tent or groundcloth and the pad survived without a pop.