A lot of outdoor gear is billed as "The only (insert product here) you'll ever need", and while that kind of statement can only be so true, Patagonia gets pretty much as close to the mark as you can with the Nano-Air Insulated Jacket. Designed as an active insulating layer for high-output alpine missions in cold weather, this jacket delivers toasty warmth, breathable performance, and ultimate next-to-skin comfort that'll make you want to keep rocking it around town long after you've put your ice axes, skins, or crampons away. And while Patagonia has expanded their Nano-Air line to feature lighter and more hybrid jackets, the original jacket still stands as the warmest and most versatile for all cold-weather activities. The Nano-Air thrives during heart-pumping and heat-building pursuits thanks two factors--its innovative Full Range insulation and its air-permeable face fabric. The jacket's fabric is not only durable, snag-resistant, stretchy, and super-soft, but also allows for just the right amount of air to get in and out so that your heat won't stay trapped inside your jacket. Now, breathable shell fabrics are all well and good, but when you're dealing with an insulating piece you've got to make sure that the technology inside is up to snuff to really call it an active piece. Patagonia understands this too, which is why they developed FullRange insulation. FullRange is light and stretchy as you move up the skin track or ice-route, but also allows your heat to escape so you can maintain a comfortable internal temperature and avoid layering and un-layering as you make your ascent. Throw on a DWR (Durable Water Repellent) coating to keep you dry against steady snowfall, and you've got versatile piece that will join you on any and all winter adventures.