Ounces count when you are ice climbing, mountaineering, or just doing your outdoors thing as hard as humanly possible in the winter. The Mammut Men's Broad Peak Light IS Down Jacket is a good choice for two reasons: it's ultra warm and weighs just over ten ounces. This lightweight down jacket is crafted from a Pertex Microlight fabric, so it's durable, breathable, and water resistant. The 850 fill goose down keeps you extra warm at basecamp or when the wind is screaming like a banshee. The jacket can be worn as either an outer layer or an under layer because of the close fitting athletic cut. Mammut knows a thing or two about extreme winter sports, so they made the front zipper pockets backpack and climbing harness compatible. When you don't need the jacket, it stows in its own left pocket for easy, low bulk carrying.