Nano, as in incredibly tiny. The teeny, whisperlight Primaloft® fibers warm better and compress smaller than any other synthetic fiber, and even keep warming when wet. When worn, it's got big warmth and a small footprint. Since it's made with more than half recycled content, its carbon footprint is even smaller. Windproof, water-resistant and it weighs just about 11 oz. Front kangaroo pocket. Packs into its own secure pocket. 100% recycled poly shell. Online only. XS(0-2), S(4-6), M(8-10), L(12-14), XL(16).