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Highlights
BEST USE: Mountaineering
PERFORMANCE: Cold Climate
WEIGHT: 3lb 3oz | 1459g
COMPRESSED VOLUME: 12.6L
LOWER TEMP RATING: -20°F | -29°C
Description
Gear up for your next high altitude or colder latitude adventure with the Alpine Down Sleeping Bag. The expedition mummy fit provides ample space for winter gear, while the modified Free-Flow Zip system provides v...
Product Details
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Sea to Summit tests its sleeping bags for their temperature rating using the ISO 23537 test protocol. This test gives two key ratings: Lower Limit and Comfort Rating.
Lower Limit: The lowest temperature at which a man should stay warm.
Comfort Rating: The lowest temperature at which a woman should stay warm.
Sea to Summit Women’s-specific sleeping bags are listed using the Comfort Rating. Unisex bags are listed using the Lower Rating. For example, if the bag is rated at Lower Limit of 14°F | -10°C and Comfort rating of 27°F | -3°C, it should keep a woman warm down to 27°F | -3°C and a man warm down to 14°F | -10°C, if they are wearing warm clothes and using a good sleeping pad.
Remember: These ratings are just guidelines. Movement, weather, and your gear setup can all affect how warm you actually stay.
Pro Tip: Think of your sleeping bag, pad, and liner as a system. If you expect 28°F | -2°C weather, choose a sleeping bag rated for 23°F | -5°C, use a sleeping pad with an R-Value of 3 or more, and add a liner for extra warmth.
![Alpine Down Sleeping Bag (-20°F)](http://seatosummit.com/cdn/shop/files/AlpineDownSleepingBag-29C--20FRegular_ASL041043-050902_PRIMARY_WBG.jpg?crop=center&height=120&v=1702674673&width=120)
![Description || Alpine Down Sleeping Bag (-20°F)(](http://seatosummit.com/cdn/shop/files/alpine-down-sleeping-bag.jpg?v=1706296475&width=1500)
Description
Gear up for your next high altitude or colder latitude adventure with the Alpine Down Sleeping Bag. The expedition mummy fit provides ample space for winter gear, while the modified Free-Flow Zip system provides ventilation and versatility. Complex construction throughout and 850+ fillpower, RDS-certified non-PFAS Ultra-Dry Goose Down delivers maximum warmth retention.
Design Details
Technical Features
![](https://cld.accentuate.io/24672501/1704914091202/Technical-Blog-Icons_850-Down.png?v=1708472656722&options=w_1440)
The second highest-lofting down used in any of Sea to Summit’s sleeping bags or quilts. 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 our non-PFC Ultra-Dry Down™ treatment.
![](https://cld.accentuate.io/24672501/1704914119641/Technical-Blog-Icons_Quilt-Lock.png?v=1708472733493&options=w_1440)
The QuiltLock™ system uses the snap locks located at the shoulder and foot end of Sea to Summit sleeping bags plus the quilt footbox / quilt straps to secure a quilt to the sleeping bag. This adds thermal performance and versatility to your sleep system: your integrated quilt now works for ultralight summer adventures and turns your three-season bag into a four-season sleep system.
![](https://cld.accentuate.io/24672501/1704914077550/Technical-Blog-Icons_RDS-Certified.png?v=1708472606613&options=w_1440)
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/
![](https://cld.accentuate.io/24672501/1704914144866/non-pfas-icon.jpg?v=1724082431013&options=w_1440)
Sea to Summit sleeping bag fabrics and insulation are made without PFAS compounds. The non-PFAS DWR finish on the shell helps prevent the insulation from becoming damp if the bag comes into contact with mositure, such as tent wall condensation.
Ultra-Dry Down is a non-PFAS hydrophobic treatment that absorbs less moisture and dries more quickly. It does not affect the 'breathability' or the lifespan of the down and lasts through at least 20 washings. The down used in our sleeping bags is responsibly sourced.
Sea to Summit Dry Bags, Stuff Sacks and Compression Bags use a non-PFAS Durable Water Repellent finish to help shed water. Big River bags use a non-PFAS PU coating.
![](https://cld.accentuate.io/24672501/1704914087458/Technical-Blog-Icons-_-Free-Flow-Zipper-System_Free-Flow.png?v=1711477015459&options=w_1440)
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.
Tech specs
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Best UseMountaineering
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Comes With40D recycled, bluesign APPROVED nylon compression bag
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InsulationRDS certified, 850+ non-PFAS Ultra-Dry Down
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ShapeExpedition Mummy
-20°F Regular | -20°F Long |
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Frequently Asked questions
Can two Alpines be zipped together?
No - the Alpine is only available as a left-zipper version
Can the Alpine be used in summer?
An Alpine is really too heavy and bulky to be practical for summer use (we're skeptical of the term "4-season bag")
Is the Alpine available in a size Small?
It isn't. Because of the relatively small numbers produced, we have to stay with the two most popular sizes, Regular and Large
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