BEST USE: Ultralight Backpacking
PERFORMANCE: Warm Weather
WEIGHT: 12oz | 340g
COMPRESSED VOLUME: 1.5 liters
LOWER TEMP RATING: 40ºF | 5ºC
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 Spark Ultralight Mummy Sleeping Bag Series spans everything from an ultralight down-filled liner, to a mid-winter fast-and-light sleeping bag. Each model uses premium materials and no-frills design to provide cutting-edge performance.
Ultralight does not mean ultra-tight: The Spark mummy sleeping bags are snug but still have adequate wiggle room for the performance-oriented, backcountry user.
The second highest-lofting down used in any of Sea to Summit’s sleeping bags or quilts. 850+ Fill Power indicates that one ounce (30g) of down will re-expand to over 850 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 https://textileexchange.org/standards/responsible-down/
Despite being incredibly lightweight, the 10 Denier UL Nylon is down-proof and surprisingly durable. A DWR finish helps to shed external moisture. This fabric is part of the secret to making the Spark and Flame Down Sleeping Bag Series some of the lightest, most packable sleeping bags available today.
Sea to Summit sleeping bags do not contain PFCs.
Ultra-Dry Down™ uses a non-PFC hydrophobic treatment to ensure it absorbs less moisture and dries more quickly. The treatment does not affect the breathability or the lifespan of the down and lasts through at least 20 washings.
The down used in our sleeping bags is RDS-certified responsibly sourced.
Down and synthetic-insulated sleeping bags utilize a non-PFC DWR treatment on the shell fabric for external moisture repellency. This helps prevent the insulation from becoming damp if the sleeping bag comes into contact with condensation on a tent wall, for instance.
Best UseUltralight Backpacking
Comes WithUltra-Sil™ compression bag and storage cell
InsulationUltra-Dry Down 850+ Loft
Shell FabricUltralight 10D Nylon Shell
Zip OptionsSpark 0-II: Left-side #3 YKK zipper; Spark III-IV: #5 YKK
|40°F Regular||40°F Long||28°F Regular||28°F Long||18°F Regular||18°F Long||5°F Long||5°F Regular||Liner Long||Liner Regular|
Frequently Asked questions
Is this sleeping bag warm enough for cooler temperatures?
This sleeping bag is great for cool-weather camping and travel, especially the 5°F or 18°F models for late fall temps. For colder winter conditions, try pairing our Spark 5°F with a 3.5 R-Value sleeping pad or higher, like the Comfort Light Insulated.
Can this sleeping bag be used as a liner inside another sleeping bag?
Yes. You could use the Spark 50°F, or even the Spark 40°F to boost the performance of a bag for cold-weather use. Adding one of these to a 20°F bag might make more sense than buying a 0°F bag for occasional winter use.
Can this sleeping bag be zipped to another sleeping bag?
Yes - this sleeping bag can be zipped to a Flame sleeping bag with a full-length zipper.