How to Choose Sleeping Bags for Backpacking
Sea to Summit Ascent AcII 15 Sleeping Bag
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Keeping you warm when it's cold outside and cool when the weather warms, the Sea to Summit Ascent AcII sleeping bag does it all with high-quality down insulation and a 3-zipper system for ventilation.
Shop similar productsKey Details
Fill
750-fill-power duck down
Temperature Rating (F)
15 degrees (F)
- Ultra-Dry 750+Loft 90% Down Cluster premium duck down is certified to the Responsible Down Standard (RDS)
- Free-flow zipper system features a full-length YKK® #5 main side zipper, half-length opposite side zipper and a foot zipper to provide ventilation
- Vertical baffles over the chest prevent down from shifting when you roll over in your sleep
- Shaped hood, oversize draft collar and zipper draft tube keep the cold out and the warmth in
- Internal pocket for your phone or other small valuables
- Form a snug double sleeping bag by zipping to any Altitude Journey or Venture sleeping bag (not included)
Imported.
Temperature ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth, since many different factors contribute to your comfort while you sleep. Backpacking bags are typically rated for temperature according to an independent testing protocol—currently International Organization for Standardization (ISO) 23537, though some older items followed European Norm (EN) 13537. Testing is based on a person wearing one base layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38.
Each bag then gets 2 ratings: the Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
View all Sea to Summit Backpacking Sleeping BagsEach bag then gets 2 ratings: the Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
| Best Use | Backpacking |
|---|---|
| Tested Lower Limit | 15 degrees (F) - EN |
| Tested Comfort | 27 degrees (F) - EN |
| Temperature Rating (F) | 15 degrees (F) |
| Temperature Rating (C) | -10 degrees (C) |
| Shell | 20-denier ripstop nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | 750-fill-power duck down |
| Lining | 20-denier ripstop nylon |
| Sleeping Bag Shape | Semirectangular |
| Stuff Sack Size | Unavailable |
| Gender | Unisex |
| Sustainability | Down certified to the Responsible Down Standard (RDS) |
Buying Advice
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Most Helpful Favorable Review
Initial Impressions
Mike3 years ago
Just got this and sharing my initial impressions. I'm replacing an existing 15 degree bag, going with this one specifically because I wanted one that unzipped all the way. Speaking of the zippers, now that I've been playing around with it. I don't understand why it has 3 separate zippers. There is the main 2-way zipper along one side that stops near the bottom, and a separate zipper in the foot box. Those 2 zippers overlap and you have to back one up to get the other one started. Why not just have 1 long zipper? And then why do we need a small zipper on the other side? The problem with all these zippers that I didn't realize is that it makes it harder to stuff this thing into the stuff sack because the zippers don't bend easily and you don't want to kink them either. There are baffles along the zipper but I also worry about how much heat you lose through there, especially that weird area where the zippers overlap.
The next issue I have is around the down insulation. I don't have the stats on my existing 15 degree bag but it is noticeably loftier than this new one, so that is a concern. My other bag is also 800 down and this one advertises 750+. This bag comes with an independent testing certification sheet, which is nice. Mine says it was tested to have 90% 800 loft down, but then it also says it's 100% duck down. That seems strange because I read here on REI that duck down is limited to below 800, and for 800 and above you have to get goose down.
My last issue is the storage sack is way too small. You have to compress the bag quite a bit to get it into the storage sack. Not sure why they did that. But count on ordering a storage sack separately.
Mike
5 people found this review helpful
Most Helpful Critical Review
Initial Impressions
Mike3 years ago
Just got this and sharing my initial impressions. I'm replacing an existing 15 degree bag, going with this one specifically because I wanted one that unzipped all the way. Speaking of the zippers, now that I've been playing around with it. I don't understand why it has 3 separate zippers. There is the main 2-way zipper along one side that stops near the bottom, and a separate zipper in the foot box. Those 2 zippers overlap and you have to back one up to get the other one started. Why not just have 1 long zipper? And then why do we need a small zipper on the other side? The problem with all these zippers that I didn't realize is that it makes it harder to stuff this thing into the stuff sack because the zippers don't bend easily and you don't want to kink them either. There are baffles along the zipper but I also worry about how much heat you lose through there, especially that weird area where the zippers overlap.
The next issue I have is around the down insulation. I don't have the stats on my existing 15 degree bag but it is noticeably loftier than this new one, so that is a concern. My other bag is also 800 down and this one advertises 750+. This bag comes with an independent testing certification sheet, which is nice. Mine says it was tested to have 90% 800 loft down, but then it also says it's 100% duck down. That seems strange because I read here on REI that duck down is limited to below 800, and for 800 and above you have to get goose down.
My last issue is the storage sack is way too small. You have to compress the bag quite a bit to get it into the storage sack. Not sure why they did that. But count on ordering a storage sack separately.
Mike
5 people found this review helpful
Customer Images
Jim B.
This is the bag I should have bought the first time.
2 years ago
[This review was collected as part of a promotion.] Some things you can't cheep out on, sleeping bags are one of those things. The design is AWSOME. I have had mummy bags and I can't sleep in them, I have had cheep down bags and they don't last and smell fowl. I roll around at night, the side zippers and foot zipper make me comfortable in all positions and temps. I am 6'2" and have plenty of room. I have slept in this bag for 65f nights and down to 35f, bag keeps me warm and with the zippers works when temps are warmer too. I guide and canoe camp. I put this sleeping bag in a Sea to Summit eVent 20L compression dry bag to keep it dry and save space. I am very happy with this sleeping bag and confident camping in colder weather.
Originally posted on Sea to Summit
Mburger97
Florida
Colder than Expected at 40F
1 year ago
This bag really appealed to me because of its low weight and the wider foot box which allows you to have more room. I took this out on a 5 night trip in the Tetons and although I made sure to open up the bag each night to loft it back up, I’ve found that it’s loft is much less than I think it should be. I originally got this in a large and it was certainly much puffier than when I swapped to the regular. And obviously I don’t care about the aesthetics of the lower loft… the performance however is correlated and i was cold at 40F. It is very comfy and I like the product, I just wish it had more down.
Age:25–34
Weight:150–175 lbs.
Height:5'11"
No, I do not recommend this product
Brian E.
I finally got a chance
2 years ago
[This review was collected as part of a promotion.] I finally got a chance to use the Ascent and while I had high expectations it so far has met them. Here in California I haven’t yet taken it into really cold conditions (have the 0 degree model), but the roominess and zipper locations have really elevated the experience and for all that in a 0 degree bag, this feels very special. I bought this to replace my Nemo Disco 15 on colder trips and was hoping it would have nearly the same sense of roominess the Disco offers and it does indeed do that. Time will tell if its warmth is there with all that space but am feeling optimistic about that. Great bag!
Originally posted on Sea to Summit
Mike
Initial Impressions
3 years ago
Just got this and sharing my initial impressions. I'm replacing an existing 15 degree bag, going with this one specifically because I wanted one that unzipped all the way. Speaking of the zippers, now that I've been playing around with it. I don't understand why it has 3 separate zippers. There is the main 2-way zipper along one side that stops near the bottom, and a separate zipper in the foot box. Those 2 zippers overlap and you have to back one up to get the other one started. Why not just have 1 long zipper? And then why do we need a small zipper on the other side? The problem with all these zippers that I didn't realize is that it makes it harder to stuff this thing into the stuff sack because the zippers don't bend easily and you don't want to kink them either. There are baffles along the zipper but I also worry about how much heat you lose through there, especially that weird area where the zippers overlap. The next issue I have is around the down insulation. I don't have the stats on my existing 15 degree bag but it is noticeably loftier than this new one, so that is a concern. My other bag is also 800 down and this one advertises 750+. This bag comes with an independent testing certification sheet, which is nice. Mine says it was tested to have 90% 800 loft down, but then it also says it's 100% duck down. That seems strange because I read here on REI that duck down is limited to below 800, and for 800 and above you have to get goose down. My last issue is the storage sack is way too small. You have to compress the bag quite a bit to get it into the storage sack. Not sure why they did that. But count on ordering a storage sack separately.
Yes , I recommend this product
Ed C.
25 degree bag doesn’t keep me wsrm
2 years ago
[This review was collected as part of a promotion.] I have to 25 degree sleeping bag and it does not keep me warm. I’m touring cross country and have already used it 6 nights with lows ranging from 41 - 50 degrees. Even while wearing wool tight, long sleeve base layer, socks, and a silk cocoon liner, I am cold. I don’t feel much loft in the bag at all.
Originally posted on Sea to Summit
Eric N.
Perfect size
1 year ago
[This review was collected as part of a promotion.] I bought this as a Christmas gift for my son. He is 6'6" tall and struggled to find a high quality bag that he could fit in. This bag was perfect for him. He was thrilled to receive it!
Originally posted on Sea to Summit
CampingBen
Nice Sleeping Bag
3 years ago
Very comfortable. Also, this sleeping bag allows you to keep both of your hands outside the bag because of the side openings. I prefer to cover my upper part of my body with my down jacket!!
Age:35–44
Weight:200–225 lbs.
Height:5'8"
Yes , I recommend this product
jegash
New Jersey
cozy, comfy, on a 35 mph windy night
3 years ago
I took this bad boy on backpack the next day I bought them; luckily, the weather was apt for me to test out the comfort, durability, and the room. This sleeping bag covers all - I like the bag as it could be converted as a quilt and at the same time can be unzipped halfway at both the end of it too warm. I was contemplating whether to go sea to summit ASCII or the Nemo’s disco 15, but I did by my right choosing the right one for me. I loved it, and it’s time to put it to use to its maximum and benefit from it for a comfortable sleep in my adventures.
Age:35–44
Weight:150–175 lbs.
Height:5'7"
Yes , I recommend this product
bkbk
Denver, CO
Warm, compact, great
4 years ago
Took this bag backpacking in ~20 degree weather, with whipping wind and snow. I was actually too hot overnight in a shirt and no pants. (I do run very warm). While my buddy was freezing all night, I was too hot and because of that didn't sleep very well - but that should tell you something. Great bag, high quality. I was really after this bag because of the weight and temperature rating combo, and it delivered.
Age:25–34
Weight:175–200 lbs.
Height:6'2"
Yes , I recommend this product
Dylan B.
This is the one
1 year ago
[This review was collected as part of a promotion.] I spend way too much time diligently researching my gear purchases. After many hours (okay, days) looking for a 0 degree for backpacking, I landed on this one. I'm 100% happy with it. The liner is plush and super comfy, it packs down small, and the zippers allow to vent when it's too warm. I don't have trouble with the zippers. I am a restless sleeper and I love being able to sleep in all positions in this bag. Yes, it is 5-8 ounces heavier than the ultralight options, but so worth it. I spend 2 weeks at a time I'm the field for work and this bag makes a huge difference. I've used it at 20-40 degree temps so far. At 40 I was all the way unzipped. At 32 I had the short zipper undone. At 20 I was comfy, and I would be confident bringing this bag to 0.
Originally posted on Sea to Summit
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