A staff pick and go to for any adventure! When you need something that packs a warmer punch than fleece, the Atom AR is a durable layer that's versatile enough to transition back and forth between use as an outer shell and mid layer, depending on conditions and your needs. Significantly warmer and more protective than its fleece counterparts, this jacket has been developed with Arc'teryx's exclusive Coreloft technology--a synthetic insulation designed to trap air and retain more warmth where you need it most. And despite thick, performance-driven Coreloft insulation, this layering piece is also crafted to pack small and carry light, making it an ideal addition to your pack.