Western Mountaineering Puma MF

The Western Mountaineering Puma MF shares its five-season, -32°C rating with Western Mountaineering's Windstopper-shell expedition bags, but skips the membrane laminate in favor of a straightforward 20D MicroLite XP nylon shell. That single difference in fabric brings the total weight down to 1475 g while carrying 936 g of 850 fill-power goose down in vertical (V) baffles — a genuinely strong warmth-to-weight figure for a sub-minus-30 bag, at roughly 46 g per degree of warmth. The trade-off is wind and moisture resistance: a plain nylon shell handles neither wind-driven heat loss nor light precipitation as well as a laminated membrane would, so this bag depends more on shelter (tent, bivy) doing that job. Draft collar and draft tube seal the neck and full-length left-side zipper; the short-length cut fits users up to 167 cm. It suits expedition and high-altitude use where every extra gram matters and the user can rely on solid shelter for wind and moisture protection — less so exposed, storm-battered conditions where a windproof shell earns its extra weight.