The Nano Puff is a lighter-weight jacket that can still provide a lot of warmth, especially when you’re active. It’s made for climbing and skiing. It’s not meant to be a standalone winter jacket, but it should be worn as a part of a solid layering system.
The Nano Puff doesn’t use down, rather it’s a synthetic material of Primaloft Gold Eco to give the best weatherproofing available. It’s only a winter jacket when you wear it above and under other layers. If you use it right, it can definitely help to keep you warm, but won’t do so on its own.