Alpine ApIII -40F

$898.95 - $948.95


The Sea to Summit Alpine ApIII down mummy sleeping bag is designed for the rarefied world of high-altitude and arctic conditions. It features cutting-edge materials, the highest quality Ultra-Dry down, and complex construction. Expedition mummy sizing allows you to wear extra clothing and boot liners inside the bag.

If you are going above or beyond, the Alpine is the bag you will want to take with you.


Sea to Summit
Temperature Rating F:
-40° F
Temperature Rating C:
-40° C
Ultra-Dry Down 850+ Loft
Shell Fabric:
Water repellent NanoShell
- Regular: fits users up to 6 ft
- Long: fits users up to 6 ft 4 in
- Regular: 4 lbs 2 oz
- Long: 4 lbs 10 oz
Fill Weight:
- Regular: 44 oz
- Long: 55 oz
Compressed Volume:
- Regular: 14.7 L
- Long: 19.5 L
Circumference at Shoulders:
- Regular: 63 in
- Long: 66 in
Circumference at Hips:
- Regular: 56 in
- Long: 59 in
Circumference at Foot:
- Regular: 52 in
- Long: 57 in
Other Features:
  • ULTRA-DRY Down 850+ Loft 90% Down Cluster Premium Goose Down certified Responsible Down Standard (RDS)
  • Free-flow zipper system: one full-length YKK® #5 main zip and a half-length zip on the opposite side for ventilation
  • Expedition sizing gives you room to wear extra clothing inside the bag
  • Anatomically-shaped, oversized foot box can accommodate boot liners
  • Technical shaped hood with hidden drawcords for maximum insulation
  • An oversized draft collar which fits snugly around your shoulders
  • Internal pocket for phone / GPS / valuables
  • Includes lightweight Ultra-Sil compression bag and storage cell

All Sea to Summit sleeping bags use only down which is certified according to the Responsible Down Standard. The RDS is helping shift the entire down and feather industry towards more humane animal rearing and handling practices. Overseen by the industry leading Textile Exchange, the RDS requires independent, third-party assessments of all aspects of animal rearing and handling throughout the entire supply chain. By using only down that meets the audited requirements of the RDS, we can have confidence that each phase of the collection process has been completed with the welfare and ethical treatment of waterfowl in mind. To learn more about RDS, visit

Nano Shell™ is a 20 Denier Nylon fabric with a water-shedding DWR finish on the exterior and a microporous PU coating on the interior. This highly breathable, highly water-resistant, windproof shell fabric is used on the Sea to Summit Alpine sleeping bags and Cinder quilts, where it protects the down from external moisture even during very wet conditions.

The highest-lofting down used in any of Sea to Summit’s sleeping bags. 850+ Fill Power indicates that one ounce (30g) of down will re-expand to over 850 cubic inches after compression. Higher loft means that less down can be used to achieve the same temperature rating – important for performance sleeping bags. The loft and down quality/composition are independently tested by the International Down and Feather Laboratory (IDFL) – a copy of the certification is supplied with every Sea to Summit sleeping bag. The down is responsibly sourced and RDS certified and treated with the environmentally-friendly Ultra-Dry Down™ treatment.

The Free-Flow triple-zip design ensures your sleeping bag retains maximum warmth and efficiency when needed and multiple ventilation options when it's not. The half-zip on the right side of the bag (left side on women's bags) provides freedom of movement for both arms, additional ventilation and allows the top third of the bag to be folded down as a mini quilt when the mercury climbs higher than expected.

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