How to Choose Sleeping Bags for Backpacking
Sea to Summit Spark Ultralight Sleeping Bag Liner
This product is not available.
Built for fast-and-light adventures, this Sea to Summit Spark Ultralight sleeping bag liner is a great pick for summer overnights or boosting your sleeping bag's warmth on chillier trips.
Shop similar productsKey Details
Fill
Ultra-dry down
Temperature Rating (F)
50 degrees (F)
- 7-denier shell and 7-denier liner materials help to achieve an impressively light weight and compact packed size
- 850-fill-power down provides cozy warmth
- Sewn-through quilted construction makes this an incredibly light and compact bag
- 1/3-length zipper
- Includes lightweight Ultra-Sil™ compression bag and storage cell
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 Comfort | 50 degrees (F) - ISO |
| Temperature Rating (F) | 50 degrees (F) |
| Temperature Rating (C) | 10 degrees (C) |
| Ultralight | Yes |
| Shell | 7-denier nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | Ultra-dry down |
| Lining | 7-denier nylon |
| Sleeping Bag Shape | Mummy |
| Gender | Unisex |
Buying Advice
Review this Product
Adding a review will require a valid email for verification
Customer Images
Sarangelo
Missouri
So tiny and packable!
2 years ago
These are so light and convenient for backpacking trips. My spouse and I both bought the 50 degree bags for summer/early fall trips, and they pack down so much nicer than any of my previous bags, fluff up well to sleep, and are easy to re-pack. It ended up being too warm to crawl in for our first test, but it made a nice pad over my air mattress and I did wrap my feet under it midway through the night and they stayed nice and cozy. I can’t really speak to the zipper issues some people noted, but didn’t have any problems with test zips. Seems like it will be a great bag for the temp range and we’re looking forward to testing them again!
Weight:100–125 lbs.
Height:5'4"
Yes , I recommend this product
David D.
Top-performance UL Bag
2 years ago
[This review was collected as part of a promotion.] The tall fit is perfect for me as I'm 189cm. The mummy fit is efficient, but not constricting or uncomfortable. With the -8°c fill, it has proven perfectly comfortable at 0° this far. The compressibility and weight was a big factor for me, and this is top for UL backpacking and bikepacking in 3 season conditions thus far. For bikepacking the back for easily in my saddlebag, and firmly in my handlebar bag. The zipper is top-notch and given the manufacturer, I will expect no issues in the future.
Originally posted on Sea to Summit
Ann K.
Light weight but not durable!!!
2 years ago
[This review was collected as part of a promotion.] The sleeping bag is warm, comfortable but not durable in the long term. Quality is compromised with the light weight feature! Duck down already shedding through the shell in less than a month. Got a left handed sleeping bag and I am right handed
Originally posted on Sea to Summit
Nathan D.
Got the 50 degree version
5 years ago
Got the 50 degree version with the hopes of using it to get as light as possible for summer alpine missions. I knew going into it that even in summer, a windy cold night in the mountains would push the 50 degree bag to its limits even inside a tent; and it did. However, I was noticeably less cold than I would have been doing a true “emergency bivy” with nothing but a jacket, so I was really happy. This piece of kit is exactly what I was looking for to push the boundaries of how light I can go without being unsafe. Also, as a photographer, I feel like I can bring that extra battery, or filter kit, or lens with the weight savings.
Originally posted on Sea to Summit
Dillon
Perfect Summer Bag
6 years ago
I purchased the Spark 50 as an alternative to a quilt to use as a summer bag. It provides the perfect amount of warmth and comfort for those hot summer nights that hover around 50 degrees. This bag is incredibly light and small and it packs down substantially smaller than the seatosummit fleece liner I have and comes in at right around 8 ounces. The size and weight do require a bit of sacrifice. The 1/2 zip makes regulating temperature a little difficult if you get too warm and eliminates the possibility of using the bag as a quilt. It's also incredibly narrow and you are quite literally stuck in the mummy position but the bag does stretch incredibly well.
Originally posted on Sea to Summit
Dean G.
Great option for lightweight warmth
4 years ago
Great bag! Felt snug but not too snug to rotate in case you are a side sleeper. The material is soft and does not cling to your skin. Just used it for the first time in Wyoming for 10 days in temps ranging from 20 degrees F to 90 degrees F. At no point did I feel uncomfortable with this bag or or that I could not make necessary adjustments to accommodate the temps. Only thing worth noting was the typical down odor that does become more noticeable when the bag becomes damp. I noticed it most in the foot box area when condensation from the inside of the tent would make contact with the bag itself overnight. I've washed this bag since and its still noticeable. 9/10.
Originally posted on Sea to Summit
Sarah
Snag-horrific zipper
3 years ago
This ultralight sleeping bag itself is very comfortable and perfect for its temperature range. HOWEVER, the zipper makes this sleeping bag unusable. The zipper is so small and flimsy that itsnags every single time I use it. Because of this I have had to mend the sleeping bag material around the zipper several times due to tares and at one stage the zip separated which was very difficult to mend. I am very disappointed and although I love the sleeping bag itself, this issue makes me want to give it 0 stars if this was possible. I appreciate the ultralight weight of this bag, but for a few grams extra a more robust zipper system would make this sleeping bag 5 stars.
Originally posted on Sea to Summit
Mark A.
Great Sack but needs more down
4 years ago
Weight and volume were awesome! I did not use the accompanying compression sack as it took several minutes to stuff and was too small. I was afraid to break the feathers. I used a larger stuff sack and placed under the Bear vault which then compressed it and it made a good base. Feather distribution was disappointing as there were too many feather free spaces and I got cold on a few nights. It was ok as I wore my silks. I just used the bag for the John Muir Trail which I finished last week. Suggestion would be to add just 1 or 2oz of feathers and improve distribution even at the cost of additional weight. Also increase the size of the compression sack by 10% to facilitate stuffing.
Originally posted on Sea to Summit
Elias H.
Light, Highly Packable, Warm
2 years ago
[This review was collected as part of a promotion.] The spark series bags have yet to disappoint! Note- there are a few compromises for the best performance, like a very light gauge zipper, 1/2 zip length, and a strong taper for the feet. If you are extremely claustrophobic and like to sleep like a starfish you may want a heavier bag for comfort- but that one small issue aside this bag is incredible! I find myself bringing it along on long backcountry day missions for a little extra insurance should I need to spend an unplanned night out! It is so light and small it fits in any kit, even ultralight bikepacking gear. Would recommend this bag to anyone!
Originally posted on Sea to Summit
Alice
The most compact sleeping bag you can find on the market for its warmth
7 years ago
My previous gripe with my past sleeping bags is they take up so much room in my smaller, women's-fit pack. They aren't kidding when they say this one packs down to the size of a large grapefruit! The zipper that extends only halfway down takes a little getting used to, but doesn't bother me anymore. This is my go to sleeping bag when I want to keep my pack light and compact, and I'm amazed at how small I can compress it down every time I pack it up. Since I am a very cold sleeper, I do pair it with a thicker liner, but I haven't found anything as warm for the same weight and size. I Also secretly love the grey pattern and bright yellow color on the inside, it's nice touch to wake up to.
Originally posted on Sea to Summit
1 - 10 of 167 Reviews