Athlete Tested. Expedition Proven. It might look like a puffer, but this jacket has been put to the test in some of the harshest conditions on earth. Adapted to the high alpine as a flexible mid layer or as an uncompromising outer layer, it thrives no matter where you take it. With highly compressible, water-repellent 800-fill ProDown, you can move lighter and faster through the mountains or the daily elements. Engineered for mobility. Cut for precision. This is Summit Series. This is the Breithorn.