Arc’teryx's Alpha series is designed for top-notch climbing and alpine performance, and their “FL” represents fast and light. True to its name, the Alpha FL jacket is minimalist and lightweight, yet meticulously designed and highly protective. We took it bikepacking and trekking in the high alpine of Peru’s Cordillera Blanca and Huayhuash to test it in the Southern Hemisphere’s winter conditions. The jacket fit the bill perfectly: it was easy to carry during hot days, and provided wind protection in the bitter cold mornings and evenings and dependable shelter from rain and sleet. Below we break down the Alpha FL’s weather protection, breathability, weight, durability, fit, and more. To see how it stacks up against the competition, see our article on the best hardshell jackets.