Refined design with 750 fill down for warmth and Down Composite Mapping™ to strategically place Coreloft™ synthetic insulation in areas where moisture can buildup, and down in areas for maximum warmth. Articulated patterning and Down Contour Construction™ for a more efficient thermal performance the Arc'teryx Thorium Women's Vest is designed to be the piece in the pack for summit chills, the layer under the shell on ski days, and the just-right extra warmth over your fleece as autumn kicks in. Made from light, downproof and durable Arato™, a bio-derived material made with 60% castor bean oil, a fabric which produces the same benefits as synthetic nylon while reducing our reliance on fossil fuels this has been treated with a FC0-DWR (Durable Water Repellent) finish to repel moisture, mists, and winter damp. With a regular fit giving you room to comfortably layer under and over this vest this comfort for your core when you’re out in the cold.