Sea to Summit Spark Sleeping Bag

Sea to Summit Spark Sleeping Bag Review 2024 Edition

A simple yet highly effective sleeping bag

Redesigned and rereleased for 2024, the Sea to Summit Spark Sleeping Bag is as good as ever. This is a classic ultralight bag made with a 10d shell/liner fabric and 850 fill power down for a high warmth-to-weight ratio. It’s simple, effective, top tier, and ready to keep you toasty warm. Shop Spark. See also Women’s Spark, Spark Pro, and Ember Quilt.

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Sea to Summit Spark 15 Key Stats

  • Price: $549
  • Weight: 25.7 oz
  • Down: 850 fill power RDS Ultra Dry down
  • Fill Weight: 16.9 oz
  • Fabric: 10D nylon
  • Down Vol: 14365 in³ | Down Vol/oz: 559 in³
  • Estimated Comfort: +20 F
  • Pros: Ultralight. Minimalist feature set. Good warmth-to-weight ratio.
  • Cons: Expensive. Heavy end of ultralight. Temp rating is a bit generous.

Compare to more great options in our guide to the best sleeping bag for backpacking. Read our Spark Pro Review, and Women’s Spark Review, and Ember Quilt Review.

Construction & Features

Starting with the insulation and using the the 15F configuration for sake of discussion, you get 16.9 oz of 850 fill power RDS-certified dry down. In context of the greater marketplace, 850 is great-not-excellent, but we’d have hoped for 900+ in a bag at this price point. That being said, 850 still performs very well and there’s lots of it. The quantity of down times the fill power yields a total insulation that’s greater than your average 20 degree bag, but less than your average 15F degree.

We also appreciate the use of 10d nylon shell fabric, which saves weight while still offering sufficient durability and comfort. Many mainstream outdoor brands of comparable size to Sea to Summit shy away from thinner shell fabrics, instead opting for overkill durability at 15d or 20d, and thus catering to the lowest common denominator who are more likely to damage their gear. Not so here!

There’s lots of little design touches that make this a great backpacking sleeping bag. We nod to the mixed baffles orientation which prevents down drift and cold spots, especially for side sleepers. Also the cinchable draft tube, and zipper plow, which seems to never get stuck. Lastly, its zippers can mate with the Women’s version to make a cozy 2P hybrid bag.

Sea to Summit Spark Sleeping Bag
Sea to Summit Spark Pro sleeping bag open top

Spark vs Spark Pro vs Spark Women’s

In summary:

  • Spark Pro is the best all around due its use of 950 FP down and generous fill quantity at all temp rating gradations, but also the most expensive and we aren’t impressed by the zippers and quilt conversion
  • Spark W’s is the warmest, but also heaviest and bulkiest at each temperature rating gradation. Because you get more down fill for the same price as the unisex Spark, it is a better value. It also claims the highest warmth-to-weight ratio
  • Spark Unisex is a good all-around blend of high performance, low weight, and low bulk, but not the best on any one measurement and has the lowest warmth-to-weight ratio
  • Ember Quilt is the lightest weight, lowest bulk and best value, just remove the under-pad strap system3

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Sleeping Bag Price ($) Weight (oz) Fill Power (in³) Fill Weight (oz) Down Volume (in³) Down Vol/Total Weight (in³/oz)
Spark W 15 549 32.8 850 24.2 20570 627
Spark Pro 15 649 27.7 950 16.9 16055 580
Spark 15 549 25.7 850 16.9 14365 559
Spark W 30 449 20.6 850 13.2 11220 545
Ember 30 399 19.2 850 12.3 10455 545
Spark Pro 30 549 21.8 950 10.9 10355 475
Spark 30* 449 17.4 850 9.3 7905 454

Table sorted by warmth-to-weight ratio using the Down Vol/Total Weight (in³/oz) stat as closest approximation

  • *Spark 30 unisex is underfilled relative to its rating, has the lowest warmth-to-weight ratio, and will feel more like a 35F bag

Sea to Summit Spark Sleeping Bag Review 2024 Verdict

Choose the redesigned 2024 Sea to Summit Spark for a great all-around ultralight sleeping bag. It has a high warmth to weight ratio, minimalist feature set (yes please!), and lots of nice design touches. Biggest drawback would be the use of 850 fill power down when we’d expect 900+ in a sleeping bag at this price point. All said and done, Spark remains one of the very best sleeping bags on the market.


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