If your pursuits require a lightweight, packable, super warm alpine jacket, look no further. The North Face Men's Zephyrus Optimus Hoodie (A0NK) is perfect for highly aerobic activity. 100 gram Primaloft insulation keeps you warm even when you pour sweat into it for hours. The shoulders and hood are coated to add water resistance, and hand pockets keep you from freezing solid. This jacket is very pack able, so it doesn't take up too much space. If bagging peaks is your work, The North Face Zephyrus Optimus is the tool for the job.