The lightest, smallest high-performance sleeping bag you can buy? This new Sea To Summit Spark SP1 weighs just 12.3 oz and packs down to the size of a grapefruit. Here's the world-first review.

What It's Supposed to Do: This isn't a sleeping bag for the casual car camper. When trying to shave weight for hardcore backpacking or climbing objectives, every ounce counts. When packing light, volume matters too. At $300 for this summer sleeping bag, you're paying a premium for that weight and space saving. But, after using it throughout Southern California and in the Sierras, I can say that it's definitely worth it.

The vast majority of people will find this bag to be weight saving overkill. But, for those of us who are logging 20+ mile days in the backcountry or are climbing days-long multi-pitch routes, it's the perfect combination of warmth, weight and compactness.


How It's Supposed To Do It: There are a combination of factors at play that contribute to the Spark's minuscule size and weight. Each of these factors work together to make the warmest, lightest, and most compact sleeping bag possible. It uses a micro-weight 10D shell and 15D lining (really light nylons,) top-of-the-line, moisture-repelling 850+ loft Ultra-Dry Down, and a ⅓ length #3 YKK zipper. The shell, lining, and zipper combined weigh less than the down insulation inside — 6.3oz of down vs 6oz for the rest of the stuff.

As with most premium ultralight gear, the materials are lighter and more delicate than heavier, bulkier stuff. So long as you're not overly abusive though, this bag will hold up.


The Spark's shell and lining feel soft and delicate, but not so brittle that they'd tear with normal use. The ⅓ length zipper may take some getting used to, too. I've found that it's easiest to bunch up the lower part of the bag, then let it extend as you wiggle down into it.

The zipper is a very small gauge, so be cautious not to break it when getting in and out of the bag (just make sure to unzip it all the way so it doesn't snag).


How Does It Perform? This bag is light! And it's small! In most cases, a sleeping bag will be one of the heaviest and bulkiest items that you'll carry. That's hardly the case with the Spark SP1. It weighs the same amount as six Cliff Bars and it's the size of a grapefruit.

Weight and space savings are cyclical too. Carry less stuff: use a smaller pack. Use a smaller pack: save more weight. With this sleeping bag, you can easily get away with carrying a 30L pack on multi-day trips, so long as the use of a bear can isn't necessary. It's low volume allows you to treat it like a regular-sized item (pot, rain jacket, etc.) when packing.


Within its temperature rating of 46°, the Spark SP1 performs as expected and keeps me warm (keep in mind that everyone sleeps differently). I've used it in lower, close-to-freezing temperatures with success by wearing all of my layers (including base layers, a down jacket,) wool socks, a hat, and liner gloves to bed. If used with a bivy sack (often an essential piece of ultralight shelter gear) you can add 5-10° of warmth to the temperature rating.

Because of its low weight and volume, it could also be used as a liner bag to bolster the warmth of your main bag in frigid winter temperatures too.


An ultralight setup featuring Hyperlite Mountain Gear's UltaMid2 and the Spark SP1.

Adventure Ready? Whenever conditions permit, I will use the Spark SP1 as my go-to sleeping bag. Even with the potential that conditions may drop below its comfort rating, I know that I can layer up my clothing (that is already being worn or carried) to ensure a warm night. Its low weight and packability are impossible to ignore.

Unlike a lot of specialty, ultralight gear which is sold by boutique manufacturers (which sometimes have long construction and shipping times,) the Spark SP1 is available from major outdoor retailers such as REI and


The Spark SP1 comes with a custom-designed compression stuff sack, a cotton sack to wash the bag in, and a storage bag. Each STS Spark also comes with an IDFL (International Down and Feather Testing Laboratory) Final Test Report stating the quality, composition, and fill-power of the specific down used in each bag. It's good to know that you're getting the real deal when dropping so much money on a piece of gear.

If you're serious about moving fast and light on overnight backpacking trips then you'll need to pack accordingly. And no sleeping bag quite compares to the Sea To Summit Spark SP1.


Photos: Chris Brinlee Jr

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