The Thorium is the obvious choice for really cold days when you need the warmth of down to keep you comfortable outdoors. Designed for efficient performance, comfort and durability, it's filled with warm, airy 750-fill-power grey goose down, certified to the Responsible Down Standard (RDS). The lightweight, durable Arato™ 30 nylon shell provides good durability and a DWR treatment to repel water. Down Composite Mapping™ strategically places Coreloft™ synthetic insulation in moisture-prone areas for optimal warmth. A bio-based lining reduces petroleum use, and multiple pockets provide convenient storage.