Whether we were hiking in chilly conditions or hanging around camp at dusk, the Aconcagua Light was our stretchy second skin. “I loved how soft the ribbed lining is, and it stayed that way even after multiple washes,” says one tester, who threw it on over a sports bra after a breezy 45°F trail run in the Tetons. An 80-denier polyamide/elastane knit outer is lightweight but tough enough to handle brushes against branches and rocks, and the fitted hood has a ponytail hole (feedback was mixed on that feature). Two zippered front hand pockets are roomy enough to fit gloves and a big smartphone. The Aconcagua Light packs down to the size of a cantaloupe.