Western Mountaineering Puma StormShield Down Sleeping Bag

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Built for deep winter and storm-bound bivvies, this bag doesn’t flinch in brutal conditions.

Western Mountaineering says: 

Known by Volcanologists the world over you’d think this Puma MF was filled with high lofting lava! 9.5” of loft, 36 oz. of 850+ fill power down, two densely packed Interlocking Draft Tubes and a full down filled collar will keep you in the ring of fire till 25 below zero. Its VBlock Side Baffle provides phenomenal down control, so necessary in a bag with this much loft. You get a 64” shoulder girth so that there’s even room for layering. The MicroLite XP™ shell has superior breathability while being extremely water resistant

Our Verdict

The Western Mountaineering Puma StormShield delivers serious warmth with its 1000 fill power down and updated StormShield shell, which handles condensation and spindrift far better than older models. At 1,628g for the regular size, it’s not a featherweight, but the performance justifies every gram if you’re pushing into -30°C territory. The loft is genuinely impressive, and the V-block baffle design helps keep that insulation where it’s needed even after repeated use. The fit is generous enough for extra layers, and the full-length zip is smooth and snag-resistant.

The packed size is on the larger side, so you’ll need to plan space accordingly. Still, this bag feels purpose-built for remote, cold, and wet missions.

– Reviewed by Ultralight Outdoor Gear

Features

• Filled with 850+ Fill Power ethically-sourced premium goose down
• V-Block side baffles provides phenomenal down control and improves insulation in colder temperatures
• Full-length #5 YKK zipper provides a smooth, easy unzipping experience while saving weight
• Insulated Draft Tube blocks cold air and keeps the torso better insulated
• Durable 20 denier MicroLite XP™ outer shell stays more breathable and water resistant longer than traditional polyesters
• Fully insulated draft collar seals in inner heat without adding much weight
• Comes with ultralight stuff sack and breathable mesh storage bag

Specifications

• Weighs (Excluding Bag): 1628g
• Temp Rating: -25°F / -32°C
• Fill: 850+ Power Goose Down
• Loft: 9.5″ in
• Inside Girth (Shoulder/Hip/Foot): 64″/56″/39″ – 163/142/99cm
• Fill Weight: 36oz – 1020g
• Stuff Size: 9″x18″L

Material & Construction

• Fabric: 20D Microfiber
• Shape: Mummy

Help & advice:

• The Ultimate Guide to Lightweight Sleeping Bags
• Time-Saver Guide to Choosing a Sleeping Bag
• The EN13537 Standard
• Sleeping Bag Shapes & Sizes
• Sleeping Bag Features 1
• Sleeping Bag Features 2
• The Ultimate Guide to Lightweight Sleeping Bags