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Sea to Summit Alpine III (Regular)

Zip Side: Left
Size: Regular

The Sea to Summit Alpine III is a down sleeping bag designed for high-altitude and arctic conditions.

Featuring cutting-edge materials, the highest quality Ultra-Dry down, and a complex construction, the Sea to Summit Alpine III has been designed with expedition sizing for efficient insulation and space that allows you to wear extra clothing and boot liners inside the bag. Vertical baffles over the chest section ensure the down insulation cannot migrate or shift to the outside of the bag during sleep, creating cold spots and a side block baffle construction maintains the 60/40 fill ratio, keeping more down on the top of the bag for maximum insulation.

The ULTRA-DRY Down™ water-repellent treatment protects the down from external moisture and condensation from the inside of the bag, virtually eliminating the negative effects moisture has on down. All Sea to Summit Down Sleeping Bags use Responsible Down Standard (RDS) certified down. The Free-Flow Zip system provides a half zip on the right side of the bag to provide freedom of movement for both arms as well as additional ventilation. The full length, two-way left side zip provides easy access and extra ventilation options.

The Alpine series feature waterproof yet breathable NanoShell™ fabric provides protection from wind and moisture. The tightly sized and carefully panelled hood fits snugly around your head, allowing you to maintain maximum warmth with minimal adjustment. An oversized zipper draft tube is fitted with the lightest and stiffest anti-snag materials for effortless operation and to prevent heat loss through the zipper.

More Help? For further assistance on choosing your down sleeping bag, we have an article explaining fill power, the pros and cons of down over synthetic insulation and more info on caring for your bag available to view here: A Guide to Down Sleeping Bags.


  • Designed for extreme cold and high-altitude conditions
  • Contoured mummy shape for efficient insulation
  • Expedition sizing for extra space and layered clothing
  • Vertical chest baffles prevent down migration and cold spots
  • Side block baffle with 60/40 fill ratio keeps more down on the top of the bag for maximum insulation
  • Anatomically shaped and oversized footbox can accommodate boots
  • Free-Flow half right-side zip for freedom of movement and additional ventilation
  • RDS 850+ Loft Premium Goose ULTRA-DRY Down™ for maximum insulation value
  • Waterproof/breathable NanoShell™ fabric protects against wind and moisture
  • Snug panelled hood maintains maximum warmth with minimal adjustment
  • Oversized draft tube with anti-snag materials, prevents heat loss through zipper
  • Oversized neck draft tube with a dual adjustment system for even cinching and maximum warmth
  • YKK #5 side zip has two sliders for easy access and extra ventilation
  • Large internal security pocket
  • Includes lightweight Ultra-Sil™ compression bag for compact storage
Note: This bag is not designed to pair with another


    • Maximum body size: 183 cm
    • Inner bag length: 192 cm
    • Comfort Temperature: -29 °C
    • Comfort Temperature limit: -40 °C
    • Extreme temperature limit: -68 °C
    • Maximum inner width: 80 cm 
    • Footbox width: 71 cm
    • Insulated collar: Yes
    • Main Fabric: 20D Nylon
    • Filling: 1250g of ULTRA-DRY Treated down 
    • Fill power 850+ cuin

    Weight: 1870g

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