Alpinists obsessed with their gear's weight got their light and warm wish when Patagonia first released the Men's Nano Puff Pullover, and it is now a go to layering piece in places ranging from K2 to Devil's Tower. The Deluge DWR finish on the 100% recycled polyester ripstop shell makes this lightweight layer both windproof and waterproof. The Nano Puff is constructed with compressible 60g Primaloft One insulation, which makes this jacket an ideal outer layer during morning belays or a midlayer while you head out for a cold backcountry tour. The Nano Puff has become a classic item because it offers essential features in a minimalist design. The brick quilting pattern, with horizontal quilt lines on side panels, prevents cold channels and insulation shift. Additionally, the elasticized cuffs and hem seal out the cold. If you start working up some heat on your tour, venting is a breeze with the deep center front zipper the zipper also has a wicking interior storm flap and zipper garage at chin for next to skin comfort. When the weather warms up, you can compress the jacket into the left chest pocket, which doubles as a self stuff sack, and then use the reinforced carabiner clip in loop to clip it to your bag. Easy. Simple. Essential.