As summer heat starts to wane, outdoor adventures remain plentiful. On its own or under a shell, the Patagonia Women’s Nano Puff Insulated Vest provides lightweight, compressible, and windproof insulation for your fall follies. The physical structure of PrimaLoft One insulation mimics the structure of feathers, trapping warm air as it leaves your body and creating a thermal barrier between surrounding cooler air and your body. Likewise, the warmth-to-weight ratio for PrimaLoft One is similar to down in that it offers substantive warmth without substantive weight. However, unlike down, PrimaLoft One only loses 4% of its insulating capacity when wet, which makes this vest an ideal choice when moisture may be factor.Along the insulation spectrum of Patagonia’s puffy vests, the Nano Puff flirts with the low end in terms of warmth. When worn alone, this vest keeps your core toasty during an early October football game or when you’re cragging or simply walking between classes as leaves begin to fall. While the Deluge DWR treatment handles light drizzle, you should throw a shell over the Nano Puff vest when nasty storms and winds howl the entrance of cooler days. A zipper garage protects your chin from chafing, and the brick quilting pattern prevents the insulation from settling and creating cold zones on your body. The chest pocket doubles as a self-stuff sack so you can easy store the Puff in your tote bag or daypack.