Sea to Summit Alpine ApIII Down Sleeping Bag (-40°C)

Designed by Sea to Summit for high altitude mountaineering and arctic conditions, the contoured mummy design delivers efficient insulation, while our updated expedition sizing provides space for extra clothing to be worn inside the bag. The anatomically shaped and oversized footbox can comfortably accommodate boots when necessary.

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. A side block baffle construction maintains the 60/40 fill ratio, keeping more down on the top of the bag for maximum insulation.

• 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
• Our 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