There are two things to point out here. One, Nau has done a great job of creating a sleek down jacket without being too puffy or cumbersome. Two, the down that Nau uses is a recycled down, a development that took years and years to get right and this season they're finally releasing it to the public.
The 650-fill is a mix of goose and duck down that is sourced from reclaimed duvets and pillows and is then repurposed for outerwear use. As for the jacket, it features fully seam-sealed construction and is both waterproof and breathable on top of keeping you warm through those colder, winter days.