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Testing
Like other quality sleeping bag manufacturers, Sea to Summit tests its sleeping bags for their temperature rating using the ISO 23537 test protocol. This information is presented using the following icon:
The test produces a Lower limit (the temperature a male sleeper should use for orientation) and a Comfort Rating (the temperature a female sleeper should use for orientation). Both are printed inside the sleeping bag and published in the Tech Specs of the sleeping bag webpages.
Sea to Summit Women’s-specific sleeping bags are listed using the Comfort Rating. Unisex bags are listed using the Lower Rating.
What you need to know about the test
A unisex sleeping bag with a Lower limit of 14°F/-10°C should keep a male sleeper comfortable down to 14°F/-10°C provided the sleeper is dressed in heavyweight base layers & insulating cap, and uses a sleeping pad with an appropriate R-Value (for these conditions, at least 4.0)
The same bag will have a Comfort Rating of around 27°F/-3°C, so a woman with the same base layers, cap and sleeping pad would be comfortable down to an air temperature of 27°F/-3°C
These numbers are guidelines, not guarantees. Many factors affect the actual performance. The biggest variable is that the test manikin does not move, where a moving sleeper can draw air into a bag, or compress insulation.
Example
It’s important to think of a sleeping bag, sleeping pad and a liner as a sleep system – combine individual products appropriate for the conditions, and the system will provide the best possible night’s sleep.
If you plan on sleeping in air temperatures of 28°F/-2°C, choose a sleeping bag with a gender-appropriate rating of 23°F/-5°C, add a sleeping pad with an R-Value of 3+, and use a Reactor Liner.
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 PFAS-free Ultra-Dry Goose Down delivers maximum warmth retention.
Design Details
Technical Features
850+ Fill Power indicates that one ounce (30g) of down will re-expand to over 850 cubic inches after compression.
The higher the Fill Power, the more the down will insulate for a given weight. This means that less down can be used to achieve the same temperature rating – important for compressible performance sleeping bags.
Every Sea to Summit down sleeping bag comes with a test report from the International Down and Feather Laboratory IDFL confirming the down loft and quality. All our down is RDS certified responsibly sourced, and hydrophobically treated with a non-PFAS Ultra-Dry Down finish
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.
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
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.
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
| -29°C Regular | -29°C 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
Shipping & Returns
Free express delivery in Australia for orders over $99.99*.
For all other orders under $99.99, we charge a flat fee of $10.00 for delivery in Australia.
For more details, check out our Shipping Policy.
We do not ship to an address outside of Australia.
If you are not entirely satisfied with your order, you may be entitled to a refund of the purchase price of the Product. For more details, please check out our Refund Policy.
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