Alpine™ Down Winter Sleeping Bag (-5°F & -40°F)

This is the sleeping bag you'll be al-pining for!

$599.00 – $849.00

Size Guide

Sleeping Bag Temperature Ratings Explained

The EN Rating scale is a scientific test to determine the warmth of a sleeping bag. The test produces a Lower rating (for male sleepers) and a Comfort rating (for female sleepers). Both are listed in the features table on the product page.

A unisex sleeping bag with a Lower limit of 23ºF means a man should be comfortable down to air temperatures of 23ºF. The same bag will also have a Comfort limit, in the realm of 32°F, so a woman would be comfortable down to an air temperature of 32ºF. These ratings require a sleeping mat with an R-Value appropriate for expected ground temperatures – without this, the sleeping bag itself is unlikely to keep the sleeper warm enough.

A variety of factors impact sleeping bag warmth - the above temperatures are merely guidelines, not guarantees. It’s important to think of a sleeping bag, an appropriately insulating sleeping pad and a liner as a sleep system. For example - if you plan on sleeping in nighttime air temperatures of 27ºF / -3°C, choose a bag with a gender-appropriate rating of 23°F / -5°C, plus a sleeping mat with an R-Value of 2.5 to 3, and consider a Reactor thermal liner.


The Alpine™ down 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 a complex construction. Expedition 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.

Is the Alpine Down Sleeping Bag…?

  • A good choice for occasional cold-weather use? Yes. The Alpine -40°F's high-lofting down, technical hood, oversized draft tubs, and draft collar work well in really cold weather; an Alpine -5°F is designed for the extreme cold of alpine/expedition use. Occasional cold-weather users might look at an Ascent/Altitude paired with a Spark or Flame as an alternative.

  • Suitable for bivvies? Yes. The NanoShell™ shell fabric is windproof and highly water resistant – it will protect the Ultra-Dry Down™ from external moisture.

  • Able to be zipped to another sleeping bag? No. The Alpine is not designed to be zipped to another bag.

Read up on how the shape, construction and down quality of a sleeping bag will affect how well you sleep HERE 


Best Use



  • Very cold weather: -5°F (comfort range -5°F to 30°F)
  • Extreme weather: -40°F (comfort range -40°F to 20°F)


  • A technical mummy shape sized to allow you to wear additional clothing without compressing the down insulation.
  • An oversized foot box


  • ULTRA-DRY Down 850+ Loft 90% Down Cluster Premium Duck 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.