Bison GWS Expedition -40°C Sleeping Bag

From Denali to Aconcagua to the Himalaya, the Bison GWS is built for the most extreme mountaineering conditions on Earth—places where failure is not an option. Trusted by professional climbers and polar explorers, this bag delivers life-saving warmth and protection in the coldest, harshest environments imaginable.

With 42 oz. of premium 850+ fill power ethically sourced goose down, the Bison GWS achieves an incredible 10 inches of loft and a -40°F (-40°C) temperature rating. The Gore Infinium™ shell provides outstanding water resistance, windproof protection, and breathability—essential for surviving high-altitude storms and Arctic gales—while remaining lightweight and highly compressible.

Its V-Block Side Baffles and horizontal chest baffles keep insulation exactly where it’s needed, while double interlocking draft tubes and a fully down-filled Gore Infinium™ collar lock in precious body heat. The massive, fully insulated hood—crafted entirely from Gore Infinium™—features an integrated ruff that seals your face from the elements, even when the wind is screaming outside your tent.

Despite its extreme capability, the Bison GWS weighs only 4 lbs 10 oz (2,097 g), making it one of the lightest true -40°F expedition sleeping bags available. For high-altitude mountaineering, polar crossings, and winter expeditions where absolute warmth and protection are non-negotiable, the Bison GWS is the ultimate choice.

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
• Weather-resistant Gore Infinium shell protects against extreme wind and moisture, while maximizing inner breathability
• Two Interlocking Draft Tubes seal the sleeping bag against cold wind and help retain inner temperature
• Offset Insulated Double Draft Tubes.
• Durable, abrasion-resistant footbox lining great for storing heavy boots & alpine equipment
• Gore-Lined insulated external hood ruff seals the bag out from freezing temperatures while retaining internal heat
• Comes with ultralight stuff sack and breathable mesh storage bag
• 4 lbs. 10 oz. Total Weight

Specifications

• Shape: Mummy (w/ full collar)
• Temp Rating: -40°F
• Fill: 850+ Power Goose Down
• Color: Crimson/Black
• Country of Origin: USA
• Fabric: Gore Windstopper
• Loft: 10.5" in
• Inside Girth (shdr/hip/foot)
  • 6'0": 64"/55"/39"
  • 6'6": 64"/55"/39"
• Fill Weight
  • 6'0": 42 oz
  • 6'6": 45 oz
• Total Weight
  • 6'0": 4 lb 10 oz
  • 6'6": 4 lb 13 oz
• Stuff Size
  • 6'0": 11"x22" XXL
  • 6'6": 11"x22" XXL