Alpine Down Winter Sleeping Bag (-20°C & -40°C)
BEST USE: Mountaineering
PERFORMANCE: 4 Season
WEIGHT: 3lbs 5oz | 1500g
COMPRESSED VOLUME: 13.1 liters
Shipping & Returns
We use climate-neutral shipping with DHL GoGreen.
For orders with a value below 75€ we charge a shipping fee of 4,95€. We do not charge shipping fees for orders with a value over 75€.
All orders received by 12:00 noon on weekdays are usually shipped the same day. Later orders are usually dispatched the following working day.
Delivery time can take up to three working days Germany-wide and up to four working days for orders outside of Germany, and depends on the shipping service provider.
All orders can be returned within 14 days of purchase. However, for the sake of the environment, please make sure to keep returns as low as possible.
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 -10°C means a man should be comfortable down to air temperatures of -10°C. The same bag will also have a Comfort limit, in the realm of -3°C, so a woman would be comfortable down to an air temperature of -3°C. 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 -3°C, choose a bag with a gender-appropriate rating of -5°C, plus a sleeping mat with an R-Value of 2.5 to 3, and consider a Reactor thermal liner.
The Alpine 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.
Comes WithUltra-Sil Compression Sack & Storage Cube
InsulationUltra-Dry Down 850+ Loft
Shell FabricWater repellent NanoShell
Zip OptionsFree-Flow zipper system
|-20°C Regular||-20°C Long||-40°C Regular||-40°C Long|
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.
100% of the down used in our sleeping bags and quilts is independently certified to the Responsible Down Standard (RDS). The RDS certifies down against animal welfare requirements and tracks it from the source to the final product. The purchase of RDS certified products demonstrates demand for better animal welfare practices in the down and feather supply chain. Sea to Summit is certified to the RDS. To learn more about RDS visit https://textileexchange.org/standards/responsible-down/
Ultra-Dry Down is a non-PFC treatment hydrophobic treatment applied to the down during down processing. It is not a coating (which would reduce the ability of the down to loft), it comprises of very small particles of a polymer that cause the down clusters / feathers to repel water. Ultra-Dry Down is PFC and PFAS-free. Hydrophobic down is not waterproof; but it absorbs less water than untreated down and dries much more quickly.
Ultra-Dry Down does not affect the loft or lifespan of the down, or its breathability. The treatment will last through at least 20 washings.
Our 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.
Frequently Asked questions
A good choice for occasional cold-weather use?
Yes. The Alpine -40°'s high-lofting down, technical hood, oversized draft tubs, and draft collar work well in really cold weather. The Alpine -5°F is designed for the extreme cold of alpine expedition use. Occasional cold-weather users might look at an Ascent/Altitude or the ultralight Spark/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.
You have more questions?
Check out our FAQ page HERE and discover even more answers about our products.