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Western Mountaineering Puma GWS -25°F

Top 10 · Gear

The 10 Best Winter Sleeping Bags

Zero-degree and colder bags ranked on real fill quality, draft control, and moisture management.

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Winter bags fail at the details: a collar that leaks, a zipper baffle that pinches, down that wets out by night three. We ranked bags on measured fill power, draft-collar design, and shell breathability — the things that decide whether you sleep or shiver. Expedition bags from small European and North American shops beat mass-market names outright here.

Best of the Best · Head to Head

Puma GWS -25°F vs Snowbunting EX 0

#1 vs #2 — side-by-side specs, pros & cons, and the final verdict.

Topic summary

Zero-degree and colder bags ranked on real fill quality, draft control, and moisture management.

Key takeaways

  • #1 Puma GWS -25°F — Western Mountaineering
  • #2 Snowbunting EX 0 — Feathered Friends
  • #3 Bloody Mary -13°F — Valandré
  • #4 Panyam 600 — Cumulus
  • #5 Neutrino Pro 800 — Rab
  • #6 Sonic -20 — Nemo

Intended uses

Gear

Verification notes

Editorial ranked list, 10 entries. Evidence mix — 10 research only. Buy links open the maker or a retailer search.

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  1. 1
    Puma GWS -25°F by Western Mountaineering

    Puma GWS -25°F

    — Western Mountaineering

    The American benchmark. 850+ fill, continuous baffles, and a collar that seals like a gasket.

    Research onlyRead the full profile
    Buy at westernmountaineering.com Full review
    No ratings yet
  2. 2
    Snowbunting EX 0 by Feathered Friends

    Snowbunting EX 0

    — Feathered Friends

    Seattle-built, 900+ fill, Pertex Endurance shell. The most efficient warmth-to-weight bag in a winter tent.

    Research onlyRead the full profile
    Buy at featheredfriends.com Full review
    No ratings yet
  3. 3
    Bloody Mary -13°F by Valandré

    Bloody Mary -13°F

    — Valandré

    French expedition bag with a chevron baffle layout that keeps down off the cold spots. Cult favorite in the Alps.

    Research onlyRead the full profile
    Buy at valandre.com Full review
    No ratings yet
  4. 4
    Panyam 600 by Cumulus

    Panyam 600

    — Cumulus

    Polish makers building to order with Polish goose down. Fill weight and shell fabric are yours to spec.

    Research onlyRead the full profile
    Buy at cumulus.equipment Full review
    No ratings yet
  5. 5
    Neutrino Pro 800 by Rab

    Neutrino Pro 800

    — Rab

    Hydrophobic Nikwax down and a Pertex Quantum Pro shell. The go-to British bag for damp cold.

    Research onlyRead the full profile
    Buy at rab.equipment Full review
    No ratings yet
  6. 6
    Sonic -20 by Nemo

    Sonic -20

    — Nemo

    Thermo Gills let you dump heat without opening the bag. The best-ventilating winter bag made.

    Research onlyRead the full profile
    Buy at nemoequipment.com Full review
    No ratings yet
  7. 7
    CWM -40 by Marmot

    CWM -40

    — Marmot

    The classic deep-cold workhorse. Overbuilt draft tubes and a full-length two-way zip.

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    Buy at marmot.com Full review
    No ratings yet
  8. 8
    Redline -20°C by Mountain Equipment

    Redline -20°C

    — Mountain Equipment

    British down expedition bag with a hood that cinches to a coin-sized hole and stays put.

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    Buy at mountain-equipment.co.uk Full review
    No ratings yet
  9. 9
    Defence 6 by Carinthia

    Defence 6

    — Carinthia

    Austrian synthetic bag issued to alpine troops. The pick when your bag will get wet and stay wet.

    Research onlyRead the full profile
    Buy at carinthia.eu Full review
    No ratings yet
  10. 10
    Ultima Thule -20 by Wiggy's

    Ultima Thule -20

    — Wiggy's

    Lamilite continuous-filament synthetic. Bulky, indestructible, and it still insulates soaked — a bush-Alaska staple.

    Research onlyRead the full profile
    Buy at wiggys.com Full review
    No ratings yet
Bottom line

Buy 10°F colder than you expect, and buy the collar — a good draft collar is worth more than 2 ounces of extra fill. For multi-week trips, choose a vapor-permeable shell or a synthetic overbag.

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