Ascent Down Sleeping Bag (25°F, 15°F & 0°F)
BEST USE: Backpacking
PERFORMANCE: 2.5 Season
WEIGHT: 1lb 14.3oz | 860g
COMPRESSED VOLUME: 4.9 liters
Shipping & Returns
Our warehouse is actively shipping orders from 8am to 1pm MST Monday through Friday. Most orders ship in one business day, but the transit time can take up to 7 days, depending on your distance from Boulder, Colorado.
2nd Day and Next Day Air orders will ship same day if placed by 1pm MST, Monday-Friday (except holidays).
All orders are eligible for fast and easy returns within 60 days of purchase.
For more details, please check out our Help Center
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.
The second highest-lofting down used in any of Sea to Summit’s sleeping bags. 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 the environmentally-friendly Ultra-Dry Down™ treatment.
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. 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.
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/
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.
Comes WithUltra-Sil™ compression bag and storage cell
InsulationUltra-Dry Down 750+ Loft
Shell FabricLightweight 20D Nylon Shell
Zip OptionsFree-Flow zipper system
|25°F Regular||25°F Long||15°F Regular||15°F Long||0°F Regular||0°F Long|
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 25°F and 15°F true 2.5 – 3 season bags. For colder weather, you might choose the Ascent 0°F 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.