Minimalist, sleek and surprisingly warm, the heat-trapping Nano Puff® blocks wind, sheds snow and uses the best available synthetic insulation. The 100% recycled polyester ripstop shell glides effortlessly, whether worn as an outer or midlayer. It's weather-resistant and windproof enough to wear as an insulated shell in a gusty snowstorm, trim enough to pull on for chilly rock pitches (and still see your footholds), and warm enough for light belay parka duty on quick alpine dashes. Low-bulk, hydrophobic, highly compressible PrimaLoft® One (60-g) insulation traps heat with remarkable efficiency, even when wet. The Nano packs down to practically nothing and stuffs into a single chest pocket that has a carabiner clip-in loop. Elasticized cuffs and hem seal out wind and trap warmth.