Part of Arc'teryx's premium Down Series the Thorium AR beefs up the warmth and efficiency, creating a substantial layer which has a high quality down core. Offering reliable down warmth throughout the colder months, this jacket uses a durable baffled face fabric to protect 750 fill goose down insulation which seals in valuable body heat. The strategic placement of synthetic insulation in the hood, cuffs and underarms means that areas prone to contact with moisture remain warm.