How to Choose Sleeping Bags for Backpacking
Sea to Summit Spark SpI Sleeping Bag
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Packing down to the size of a 1-liter water bottle, this ultralight bag balances size, weight and warmth to make it an excellent choice for summertime backpacking, cycle touring and mountaineering.
Shop similar productsKey Details
Fill
850-fill goose down
Compressed Volume
1.55 liters
Temperature Rating (F)
46 degrees (F)
- High-loft, premium 850-fill-power European goose down offers superb warmth with minimal weight; Ultra-Dry Downâ„¢ water-repellent treatment protects down from moisture
- Ultra-Dry Down is a water-repellent polymer treatment applied to the down; Ultra-Dry Down retains 60% more loft and absorbs 30% less moisture than untreated down
- With a European Norm (EN) lower-limit rating of 46°F, the Sea to Summit Spark SpI will help keep you warm on 3-season backpacking adventures in warm weather
- You can also use the Spark Sp I as a booster bag by slipping it inside another sleeping bag to add warmth
- Ultralight 10-denier Pertex® Quantum® fabric with a durable water repellent treatment sheds moisture
- Soft 15-denier nylon fabric lines the sleeping bag for excellent comfort next to skin
- Left-side 1/3-length zipper saves weight over a full-length zipper
- Compresses to the size of a grapefruit
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 Mountaineering |
|---|---|
| Tested Lower Limit | 46 degrees (F) - EN |
| Tested Comfort | 54 degrees (F) - EN |
| Temperature Rating (F) | 46 degrees (F) |
| Temperature Rating (C) | 8 degrees (C) |
| Ultralight | Yes |
| Shell | Ripstop nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | 850-fill goose down |
| Lining | Nylon |
| Sleeping Bag Shape | Mummy |
| Stuff Sack Size | 4 x 9 inches |
| Stuff Sack Volume | 2.5 liters |
| Compressed Volume | 1.55 liters |
| Gender | Unisex |
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Customer Images
Compass
Marietta, GA
My go-to sleeping bag!
10 years ago
I've had this bag for over a year now, and this is definitely my go-to sleeping bag. Even when the temps drop past the 46 degree rating, I just add thermals and a down jacket. This bag weighs 14 ounces... that's just insane. You can't go wrong with this bag. I will agree the cut is tight, but helps keep in the warmth. I highly recommend you pick this bag up... you won't regret it.
Yes , I recommend this product
ClimbSkiSail
Portland, OR, United States
Incredibly Small
10 years ago
First a disclaimer, I have only tried this bag out indoors because I may need to exchange it. It is amazingly small and light. Taking the sleeping bag out of the stuff sack is like pulling a rabbit out of a hat. It's incredible how well it packs down. BUT... this may come at the cost of warmth. The bag is practically see-through. It is warm for how thin it is, but I may exchange it for the *Sea to Summit SPII*, which is also small, but 10 degrees warmer. Another note, I usually feel claustrophobic in mummy bags, so I was worried about the shape of this bag and 1/3 zipper, but it was actually extremely comfortable. It is shaped very well.
Yes , I recommend this product
James Paul
Indianapolis, IN, United States
Constrained Quality
10 years ago
The quality of this bag is great, and it's warm. I thought I'd try the mummy bag, but it was unfortunately too constraining at the feet. I also didn't notice that the zipper doesn't go all the way down. So I thought I could open it on warmer nights to get some more foot room, but that's not possible. For someone who doesn't mind the lack of room around the legs and feet, this would be a great bag. It's super light, and it's put together very well. But I'm going to try the Sea to Summit Trek for some extra leg room.
Yes , I recommend this product
LessGearMoreBeer
VA
Great Bag with a Great Weight
9 years ago
I have only used this one night so far, but it was great. The temps were right around the 45 degree mark and I was actually a bit too warm. (I am a very hot sleeper and I was sleeping on a NeoAir X-Light). The size is amazing as it stuffs down to about 2/3 the size of a nalgene bottle. I am 5'11 and opted for the long bag. I think I would have been fine with the normal one.
ivnosliwb
WA
Design changes?
11 years ago
Received package very, very, very fast! Product appears to match specs. However, I was surprised to see that the product photo doesn't match the product in my hands. The logo is not on the silver side. Product contents tag is on the silver side. Zipper back side appears to be on the silver side. So overall it seems like the silver side is now the inside? And the orange side is now the outside? So confusing. If this is the case I think it actually looks better. The only thing that concerns me is the fabric on one side is more durable so I want to make sure I use the correct side. Overall very happy. I haven't tested it yet but everything appears to be well made as expected.
Yes , I recommend this product
Chuck
Kentucky, United States
Sea to summit
8 years ago
We bought these for bike packing. They are very light weight and pack up very small. The only thing I would do to make it better would be another zipper or a longer zipper.
Yes , I recommend this product
eclaywhite
Charleston, SC
nice but restricting
6 years ago
This is a great bag for what it is. It packs down incredibly, astonishingly small, and you barely notice that it's in your bag. It is comfortable and if you always keep your bag fully zipped over your legs or don't mind keeping your feet in the bag then you will enjoy it. The feature that causes my only bit of dissatisfaction is the lack of a full side zip. I have found while using this that I need the full length zipper in case I get too hot and need to kick my feet out. I plan to return it since I have gravitated away from using it after a few months of trying to find comfort and try an ultralight quilt this time. I would probably have kept this bag if the zipper was full-length. They should attempt to find a way to maintain the small pack size with a full-length zipper.
Yes , I recommend this product
Mule
Shiznizzle
Perfect for warm-weather use
8 years ago
Finally had the chance to try this bag for a couple nights. Temps were in the low 50º F range, and the Spark SPI was plenty warm for those conditions. I didn't even have to zip it up fully, and was comfortable sleeping in boxers. I can definitely see myself being comfortable into the high 40's (Farenheight) with no problem, and if I wanted to go lower I could easily wear layers and/or use a bag liner for extra warmth. The bag is amazingly light, well-constructed, and compresses so small that you could almost hacky-sack with it. :-) It would be nice if the zipper went a bit lower, and was of a more sturdy gauge... but it hasn't given me any problems, and I guess that these are the details that allow this bag to weigh in at under a pound. It's beautifully constructed, very well done. This will be my go-to 3-season bag from now on; I will simply supplement with a bag liner and merino long underwear if necessary. Great bag!
Yes , I recommend this product
Coach Rev
Gothenburg NE
short side zip a real problem
8 years ago
for a tall guy like me, the short zipper is problematic. I ended up exchanging this bag as a result, without ever using it. Everything else (weight, compressability, etc) seemed good, and if you don't mind shimmying into your bag from the top, this would likely work for you. Just not for me.
No, I do not recommend this product
éthan
Minnesota
Amazing!
7 years ago
Bought this a few months ago as I wanted a new summer bag (bought the sea to summit extreme liner to make it a three season as I live in Minnesota) and I am STILL blown away with how small it packs, how little it weighs, and how warm it is! Used in Michigan UP and it dropped to about 40 degrees and was perfectly comfortable!
Yes , I recommend this product