Compact and superlight, Arcteryx's lightest Atom vest easily stashes in your pack, ready to grab when summer temperatures drop. Worn as a midlayer or standalone, it delivers moderate insulation perfect for early morning runs and taking in the view from a freshly bagged peak. The Tyono™ 20 shell balances breathability and wind resistance, and the Coreloft™ insulation is light, compressible, and efficient. Lightweight stretch fleece side panels improve ventilation and hold the fit.