The Arc'teryx Delta AR zip top provides superb insulation as part of an effective layering system. Polartec Thermal Pro high loft grid fabric supplies superb warmth for its weight, & the trim fit helps to wick moisture effectively & makes for easy layering. The longer cut & DWR finish combine to help keep light rain & wind at bay. Glossary Polartec Thermal Pro: Fleece fabric designed to manage perspiration, add warmth & resist weather, ensuring a comfortable climate between body & clothing layers. Wick/ Wicking: The act of transferring moisture from the skin to the outer layer of a garment quickly & efficiently, where it evaporates. Provides a drier more comfortable environment inside a piece of clothing.DWR (Durable Water Repellent)A DWR treated fabric will bead-up water on its surface to stop it soaking into the fibres. This maintains breathability & shortens drying times.