Never worn, new without tags The Atom is the ultimate outdoor kit essential, delivering reliable, breathable warmth for chilly alpine starts and unexpected summit squalls. Built with lightweight Coreloft insulation that won't pack out (even after years of wear) and stretchy fleece side panels, it traps and dumps heat strategically. Slide it under a hardshell for a clutch layering system that'll keep you warm, even if it gets wet.