The Arcteryx SL Hoody boasts one of the best weight-to-warmth ratio out there! The ultra-light construction is both wind resistant and breathable. The durable outer material made of Tyono 20 fabric with a durably water-repellent DWR treatment is robust and serves to protect the insulation from moisture. For optimal freedom of movement, the jacket has been equipped with Torrent fleece stretch panels, which are very elastic and odour-resistant to boot, thanks to the Polygiene treatment. For warmth in the Atom SL Hoody, Arcteryx used the Coreloft Compact 40 synthetic insulation. In addition, the siliconised polyester fibres will quickly and reliably repel moisture. Even when wet, the fibres will hardly lose any of their thermal efficiency. The jacket is slim-fitting, which serves to increase breathability during strenuous activity. The hood is not insulated and thus can only provide light protection against the wind.