Light, versatile synthetic insulated jacket works as a midlayer and standalone. Atom Series: Synthetic insulated midlayers. Performing as midlayer and standalone across a broad range of activities and output levels, the iconic Atom is an Arc‘teryx mainstay. Over time, we have refined the design to elevate performance, improve durability and extend its versatility. Its Coreloft™ Compact insulation retains heat when wet and withstands repeated packing and unpacking. Light, soft and durable, the Tyono™ 20 face fabric resists wind and weather, and stretch fleece side panels improve ventilation and freedom of movement.