BEST USE: Backpacking
PERFORMANCE: 2.5 Season
WEIGHT: 1lb 14.3oz | 860g
COMPRESSED VOLUME: 4.9 liters
Shipping & Returns
Free express delivery in Australia for orders over $49.99*.
For all other orders under $49.99, we charge a flat fee of $10.00 for delivery in Australia.
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We do not ship to an address outside of Australia.
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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 14ºF means a man should be comfortable down to air temperatures of 14ºF. The same bag will also have a Comfort limit, in the realm of 27°F, so a woman would be comfortable down to an air temperature of 27ºF. 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 Ascent down mummy sleeping bag redefines the meaning of versatile. Complex construction and high-quality down keep you warm when it's cold outside, while the triple-zipper Free-Flow Zip system ensures you stay cool and ventilated when the weather warms.
Shaped to allow a natural sleeping position for comfort, while light and compact enough to go anywhere.
Comes WithUltra-Sil compression bag and storage cell
InsulationUltra-Dry Down 750+ Loft
Shell FabricLightweight 20D Nylon Shell
Zip OptionsFree-Flow zipper system
|Ascent I (-4°C) Regular
|Ascent I (-4°C) Long
|Ascent II (-10°C) Regular
|Ascent II (-10°C) Long
|Ascent III (-18°C) Regular
|Ascent III (-18°C) Long
The second highest-lofting down used in any of Sea to Summit’s sleeping bags or quilts. 750+ Fill Power indicates that one ounce (30g) of down will re-expand to over 750 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.
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
Down and synthetic bags identified with our zip coupling symbol use a 65 inch #5 YKK full-length zip which allows a unisex left-handed and women's specific right-handed bag to pair together. Designed to pair side by side, each person sleeps in their own bag enabling each of you to take advantage of your bag's unique insulation zones, hood and footbox features - perfect for cozy adventures for two. Bags with full-length #5 YKK zips on both sides can also be coupled together with other pairing bags.
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.
Sea to Summit hydrophobic down and DWR finishes are Non-PFC.
The down is RDS-certified responsibly sourced. The non-PFC Ultra-Dry Down™ hydrophobic treatment means 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
Non-PFC DWR Shell fabric:
Despite being incredibly lightweight, the 10 Denier UL Nylon is down-proof and surprisingly durable. A non-PFC DWR finish helps the shell to shed external moisture. This fabric is part of the secret to making the Spark and Flame Down Sleeping Bags and the Ember Quilt Series some of the lightest, most packable sleep system products available today.
Frequently Asked questions
Warm enough for cold-weather use?
Yes. The high-lofting down, technical hood, oversized draft tubes, and draft collar make the Ascent -4°C and -10°C true 2.5 – 3 season bags. For colder weather, you might choose the Ascent -18°C and pair it with a greater than 3.5 R-Value sleeping mat like the Comfort Light Insulated.
Really cool in summer temperatures?
Yes. The Free-Flow Zip system means separate zippers on your left and right side and in the foot box. Open them for ventilation or to turn the Ascent into a comforter.
Able to be zipped to another sleeping bag?
The main side zipper can be zipped to the Sea to Summit Women’s Altitude, Journey and Venture sleeping bags. The Ascent Regular and Long bags have the same side zipper length.