Patagonia made the 10-ounce Men's Down Sweater for alpinists, ice climbers, and backcountry skiers who need insulation that weighs as little as possible. Although the Down Sweater weighs less than most fleece jackets, its 800-fill down insulation provides far more warmth. The ultralight DWR-coated 22D polyester shell protects the insulation from moisture. This Patagonia jacket packs so small that it fits in its own interior pocket, which makes it a great choice for climbs where pack size must remain minimal.