Compact and superlight, their 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. The Atom Lightweight Vest was previously the Atom SL Vest.