Lightweight with an endlessly versatile design, the Arc'teryx Men's Atom Vest uses lightweight and sustainable Flortius™ Air 20 for durable comfort from season to season. Constructed with Coreloft™ stretch insulation and lined with durable nylon plain weave, this fitted midlayer makes the most out of its terrain. Ergonomic in its design and packable for convenience, the Octa® Fleece sides enhance mobility while allowing comforting ventilation.