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Sea To Summit Spark Sp II Review

Backpacking Sleeping Bag

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Price:   Varies from $329 - $379 online  —  Compare at 4 sellers
Pros:  Super light, highly compressible, available from major online retailers
Cons:  Patchy cold spots, not versatile
Editors' Rating:     
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Manufacturer:   Sea to Summit


Our testers love the Sea to Summit Spark Sp II sleeping bag when they want to save weight and space in their pack. We found it to be an appropriate summer bag for middle elevation mountain terrain. We didn't think twice about carrying it for trips where we wanted to move fast and carry less weight. For a specialty sleeping bag, the price tag is fair, but don't count on this bag doing it all. The window of time for which it will be comfortable is limited. If you're going to spend more time carrying your sleeping bag than sleeping in it, consider a super light bag like the Sea to Summit Spark Sp II. For a more well-rounded three season sleeping bag, take a look at our Editors' Choice winner, the Western Mountaineering Ultralite or our complete Backpacking Sleeping Bag Review for better options.

RELATED: Our complete review of backpacking sleeping bags

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Analysis and Hands-on Test Findings

Review by:
Mike Phillips
Review Editor

Last Updated:
November 22, 2015
The Sea to Summit Spark Sp II is a surprisingly warm 1 pound sleeping bag. This minimalist model is a great choice for backpackers and climbers looking to save weight and pack space for specific mountain objectives. This bag is an excellent option for the specific application of fast and light backpacking.

Performance Comparison

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The longer and more ambitious your backpacking objective is the more important spending a little extra to buy a lighter wight sleeping bag becomes. Here two lightweight backpacking bags out for a side-by-side comparison along the John Muir Trail.


The Spark Sp II is much warmer than we expected a minimalist bag to be. It is shockingly light for a traditional mummy style sleeping bag. It feels like a cloud in your hands, and the white color makes that feeling even more convincing. You can literally see the down through the nearly translucent exterior fabric and it is obvious that the down is of high quality as you feel the bag and look at the healthy down clusters inside. By looking through the exterior, you can also see why the Spark Sp II felt like it had patchy cold spots. Down needs to be shifted around inside the baffles to maximize the distribution of the insulation. There is proportionally more down near the core of the body, just where you need it most to stay the warmest.

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The ghostly white, lightest fabric-in-the-review 10D shell material of the Sea to Summit Sp III reveals the high quality down within. This incredible light material was somewhat water resistant and more durable than our testers anticipated. It handled condensation in the tent and from dewy nights quite well and as of yet hasn't leaked any down.


The Sea to Summit Spark Sp II weighs an incredible 18oz. in a size long. It accomplishes this by featuring a slim fit, lightweight fabrics inside and out, a ⅓ length zipper, and 850+ fill down. There really isn't anything else to this bag. It is overall very simple in design, and weight and space are the primary considerations for anything that is part of the Spark Sp II. The only bags featured in our Backpacking Sleeping Bag Review that compare weight wise are the more expensive Marmot Plasma 30 and the less warm and less comfortable minimal Western Mountaineering Highlite. You can explore our Ultralight Sleeping Bag Review for other non-traditional sleeping bags that are more in the league weight wise with the Sea to Summit Spark Sp II.

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The hood on the Spark SP II fits low on the face and has big gaps for warm air to escape. There is also no draft collar on this sleeping bag.


Soft materials and soft, high loft down make the Spark a reasonably comfortable bag. It features a slim fit that allows little room for thrashing about inside the bag. However, it fits close enough that it is easy to move with the sleeping bag. It does have a hood, which adds a bit of warmth and comfort over a hoodless ultralight design.

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The Sea to Summit Spark Sp II has the most slim cut of all of the bags in our backpacking sleeping bag review.

Packed Size

Sea to Summit provides a great sil-nylon compression sack with the Spark Sp II. An especially small bag, it is important to be able to get the sleeping bag as small as possible. All packed up, it's smaller than a football; making it really easy to squeeze into the corner of a very small pack.


The standout features of the Sea to Summit Sp II are the high quality materials it is constructed from. The shell of the bag is made from 10 denier Pertex Quantum fabric for minimal weight and bulk. We like how the DWR treatment shed condensation on the outside of the bag. 850+ fill down is the insulation of choice for lightweight sleeping bags like the Spark. Appropriate attention was paid to minimizing extra features so as to keep the weight down. Extras on this bag mean that things were taken away. The ⅓ length zipper, the slim cut, and the small diameter drawcord at the collar are all examples of this bag's minimalism.

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The Sea to Summit Spark SP II out for a warm night under the stars beneath Banner Peak in the High Sierra.


Extra lightweight sleeping bags like the Spark Sp II are less versatile than general backpacking sleeping bags. Their minimalist design will not stand up to prolonged use in tough conditions year after year. We felt less than inspired going to bed when we used this bag on cold nights. Unless you sleep really warm or you're very tolerant for a restless night, we don't think the Sp II will hold up for shoulder season trips. If you want a warmer and more versatile bag, check out our Editors' Choice winner, the Western Mountaineering Ultralite or the slightly roomier Western Mountaineering Alpinlite. Both of these bags are lightweight and high quality, but warm enough to be used during shoulder seasons.

Best Application

The Spark Sp II is best suited for specific mountain objectives where weight and space in your pack matters most. If packed size and weight are the most important variables you consider in a sleeping bag, this bag excels as a small, light summer option.


Other approx. one pound sleeping bags like the Western Mountaineering Highlite are comparable in price to the Sea to Summit Spark Sp II. The other contender for the lightest traditional mummy style sleeping bag in our review is the Marmot Plasma 30, which costs 240 dollars more! We consider all of these bags to be specialty sleeping bags that have a unique purpose in your backcountry gear quiver. If you are invested in lightening your pack for those special big trips, consider buying a lightweight bag like the Spark. If you are looking for a sleeping bag for versatility try the warmer Western Mountaineering Ultralite or Alpinlite.

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The Sea to Summit Spark SP II is a lightweight traditional style sleeping bag that is best for ultra-light backpacking and alpine climbing trips.


The Sea to Summit Spark Sp II is a super light, smartly featured, minimalist sleeping bag. It should be used for light and fast missions in the mountains where every ounce and every cubic inch matter. Well-insulated for a lightweight summer sleeping bag, the Spark is right at home in mid-elevation terrain. We recommend this bag for users who already have a three season sleeping bag that is their all-purpose workhorse and need an ultra-light bag for specific mountain trips. It is a better value than the other super light bags in this backpacking sleeping bag review. It is high quality, high performance, and a great value in this realm.

Other Versions

The Spark Sp II is part of a series of sleeping bags from Sea to Summit. They are similar in cut and the materials are the same as Spark Sp II.

Spark SP I
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  • 46*F Version of the Spark lineup
  • 12.3oz
  • $300

Spark SP III
  • 25*F Version
  • 1lbs 6oz
  • $460
Mike Phillips

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Most recent review: November 22, 2015
Summary of All Ratings

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Seller Price
Amazon $329.00  -  8% off!
Backcountry $358.95
REI $359.00
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Helpful Buying Tips
How to Choose the Best Backpacking Sleeping Bag - Click for details
 How to Choose the Best Backpacking Sleeping Bag

by Ian Nicholson, Mike Phillips, Max Neale