Sea to Summit Spark 40F
The Sea to Summit Spark 40 is a seriously lightweight and stripped down sleeping bag good for temperatures above 40F. I pair it with an Aeros pillow for a good night’s sleep.
Sea to Summit Spark 40F Specs
MSRP: $339
Bag Weight: 12.4 ounces
Fill Weight: 6.3 ounces
Shell Fabric: Ultralight 10D nylon shell and 7D liner
Length: 6 feet, regular; 6 feet, 6 inches, long
About The Spark
This Spark checks the boxes for backpackers serious about counting ounces. At 12.4 ounces and a compressed volume of 1.5 liters, this bag weighs less than a filled water bottle and packs small. The bag is roomy, although the one-third length zipper in the Spark 40F makes it a bit harder to slide in and out of the bag. There are no draft tubes, but they aren’t needed because the bag is for warmer weather. This is the bag I have been searching for to get my base weight at 10 pounds for warm weather backpacking.
Breaking Down The Spark
Fabric: UL 10 denier nylon shell with a 7 denier liner. The outer material is very light, but it shouldn’t be a problem as long as you’re sleeping on a pad and not the rocky, stick-covered ground. The inner lining is incredibly light. The Spark uses a sewn-through design to reduce the bag’s weight, but that also means cold air can seep in at the lower end of the temperature rating.
Insulation: 850+ loft ultra-dry down, the upper end of loft for sleeping bags, gives the Spark good warmth for less weight. The insulation puffs up nicely, and dried quickly after getting damp inside my tent during a nighttime rainstorm. The down adheres to the Responsible Down Standard.
Zipper, Adjustable Mummy Hood: The left-side zipper slides easily without snagging, mainly because there is no draft tube and no bulky filling to overlap the zipper. The one-third length zipper can be annoying when getting in and out of the bag, but that’s the trade-off for cutting weight. The hood is small and adjusts easily with a drawstring. I tuck my Sea to Summit small Aeros Pillow inside the hood for a good night’s sleep.
Mummy bag or quilt? It’s personal preference. I favor mummy bags for the hood that I can close off, letting me breathe outside the bag and keeping air from sliding inside the bag at my shoulders when the temperature drops. And bonus points for the Spark’s weight, which is less than some quilts in the 40F range.
Accessories: The Ultra-Sil compression sack included with the 40F Spark is very small, and I found the bag difficult to fit inside. I use a larger Sea to Summit compression dry sack, which also has room for my Aeros pillow. Sea to Summit is currently including a full-size Aeros inflatable pillow with its sleeping bags. The Spark also comes with a zippered, partial mesh storage bag.
The Spark Series: The Spark sleeping bags are available with four temperature ratings: 40F, 28F, 18F, and 5F. All are lightweight for their temperature class.
Warranty: Lifetime protection against defects in workmanship and materials to the original owner for the intended life of the product under normal use, with proof of purchase from an authorized Sea to Summit retailer.
Point of Manufacture: Vietnam
Spark Pros
Size: Lots of room inside. I’m 5 feet, 10 inches, 160 pounds, and have plenty of space inside the regular bag.
Weight: 12.4 ounces. If you’re backpacking in warmer weather, this is a great lightweight bag that packs small inside a backpack. The Spark helped me push my base weight into ultralight territory without sacrificing comfort and quality.
Warmth: I stayed warm with the Spark fully zipped and the hood tightened when the temperature dropped to around 40, and on warmer nights I slid the zipper to its maximum open position.
Spark Cons
One-Third Length Zipper: It takes extra effort to get in and out of the bag because of the one-third length zipper. And when the weather is warm, it would be nice to have a full zipper for better ventilation. But as with most lightweight gear, a shorter zipper is a trade-off for less weight, which I’m willing to accept.
Seasonal Versatility: None. This is strictly a warm weather bag, good for temperatures 40F and above. The Spark is not a shoulder season bag.
Storage: There’s no fabric loop at the foot of the bag to hang it upside down when the bag isn’t being used, but again this is a trade-off for an ultralight bag. I hang the bag using the hood drawstring; the Spark can also be stored in the mesh bag that Sea to Summit provides.
Overall Value
The Spark, at $339 MSRP, is an excellent ultralight bag for backpackers serious about traveling light in warm weather. The price is the lowest I’ve found for a mummy bag this light with quality materials, and the warmth to weight is exceptional. The Spark is lighter than some 40F quilts and competitively priced.
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This product was donated for purpose of review.