• Weight (regular) 665 grams
  • Recommended Maximum User Height 183 cm
  • Female Comfort Rating -2
  • Male Comfort Rating -8
  • Cost $799.00

Sea to Summit Spark SPIII Sleeping Bag Regular

Sleep Systems


Rating: 8.4 / 10
Weight 1.8 / 2
Value for Money 1.7 / 2
Durability 1.6 / 2
Warmth 1.7 / 2
Versatility 1.6 / 2

Sea to Summit Spark SPIII Sleeping Bag Regular Review

For a number of years I scanned the internet for a new cold weather sleeping bag. Apart from keeping me warm in temperatures around -7° Celcius I wanted a bag that weighs very little and packs down to almost nothing. To clarify my need, I didn’t need ‘just one bag’ for all my needs year round as I already own a lighter weight option that meets my needs for when it’s warm. Achieving these criteria meant I was going to be in the upper end of the down bag price range (as opposed to the synthetic bag end).

For a while now I have had my eye on the Spark range of bags from Sea to Summit; these bags really caught my eye when they came onto the market a few years ago. The Spark bag range consists of five models (Spark 0, 1, 2, 3 and 4) which provide a varying degree of warmth from summertime to full on winter and which come in regular and long lengths to ensure you get the appropriate sized bag for your height. There can be no doubt that this bag range is aimed at serious hikers, in fact Sea to Summit advertises the Spark SPIII bag as ‘ultra-light and technical’ for those who want maximum warmth with minimum weight. This is achieved by stripping out a few features combined with the use of 850+ loft goose down.

Sea to Summit is one of a growing number of companies that use ‘ethical down’ which is a polite way of saying they don’t pluck down off living birds. This does increase the cost but is clearly a more a humane way of collecting the down. The down is also hydrophobic which means it repels water so if it gets wet, it will still keeps you warm. The biggest decision on my behalf was which model to go for.

So after two years and umming and ahhing, I finally decided that the Spark SPIII (long size) was a real contender for my ‘go to’ bag. I was lucky enough to have a regular sized bag provided to me for testing and even with the shorter than preferred length this was a great opportunity to test this bag prior to splurging on a new bag. The regular Spark SPIII suits hikers up to 183 cm in height and is a mummy bag construction. For those of you not familiar with mummy bags, they form a much snugger fit than the tapered or rectangular bags but with the snugger fit comes a warmer bag as there is less air within the bag to heat. At the time of testing, this tester weighed in at around 107 kg and am fairly broad across the shoulders; in other words I’m not a small guy. Height wise I am just over 185 cm in height, having shrunk a couple of centimetres over the past 40 years so while I can fit into the regular length bag its a bit snug. I find the regular sized bag is just too cramped in length particularly given my size 15 feet and I prefer the longer bag which suits people up to 198 cm tall and also provides a bit of extra width as well. Having said that, the width of the bag fits well even with a broad chest and my weight.

This bag can best be classed as unisex but tends to be sold to males given it is really a twin to the Flame range which is typically sold as a women’s bag. In all honesty the main difference between the two ranges is a difference in length and width with the Flame range being slightly wider in the hip area, narrower at the chest and has an extra degree of warmth aimed for women who from a physiological perspective tend to feel the cold more than men. Having said all this, I’d ignore the gender descriptions on these bags and choose the model that best fits your personal dimensions and cold tolerance.

The Spark SPIII is grey in colour with a yellow lining and in all honesty yellow is not the best colour to hide the dirt but given I use a Sea to Summit bag liner that’s probably not a major problem. When I first got this bag out of the storage sack I thought there were stains on it but it’s just that the shell is almost translucent and you are seeing the darker colour down that shows through particularly on the yellow inner lining. As an ultralight bag, the outer and inner shell use very lightweight materials (10 Denier Nylon shell and 7 Denier lining fabric) so if you are really rough with your gear then there is potential for you to tear the bag – this is not the bag you want loan to a novice hiker friend or use as a hire bag.

The Spark SPIII has all the essential features of a high end bag including draft tubes at the front of the neck and along the zip although there is only a single neck draft tube whereas in heavier weight winter bags there are usually one at the rear of the neck as well to minimise air flow. The zip on this bag is 3/4 length in an attempt to minimise weight and there is no additional toe box zip that allows the bag to flatten out into a full blown quilt like many of the heavier grade bags. The other thing that is missing is an internal security pocket for a wallet or phone which doesn’t worry me too much as I have never owned a bag with this feature in the past.

Over the past few years Sea to Summit has included a design feature on all of their higher end bags which is to have horizontal down baffles on the upper body and vertical down baffles on the lower body. This means the correct amount of down is kept on the specific area of the bag to keep you warm. As expected with an ultralight high, end bag the Spark SPIII packs down to a very tiny size. Given that sleeping bags are often one of the bulkiest items you will carry in your pack, this bag is a real space saver.

Now for the negatives. Apart form the potential to show marks and dirt the main negatives with this bag are often the things that make this bag so good. The lightweight material that is used in the construction will require you to ‘handle with care’. The fact that this bag is ultra compact and ultra lightweight (the regular sized bag weighs in at 665 grams and the large is 775 grams) also means that it is not cheap. The usual RRP is around AUD$799.00(Regular) putting it in the upper end of the non-alpine sleeping bag range. I own lightweight tents that are cheaper than this sleeping bag!

Even though I only had this Sea to Summit Spark SPIII bag on loan to test, it didn’t fail to impress and met my preconceived expectations. It packs down very small, it weighs very little and is toasty and warm which is what you would expect from a bag containing 850+ loft down. The Sea to Summit Spark SPIII bag comes in lighter weight and heavier weight versions depending on your warmth requirements.

Given the price of this bag its not going to be for everyone.  All in all, the best way to describe this bag is as a ‘technical bag’, aimed at hikers who want maximum warmth and minimum weight who want to get their pack weight as low as possible and who are willing to pay a premium price.  If that is you then this is your bag. If you aren’t in a hurry then keep an eye out for the regular sales that occur to get yourself a great deal.

We Like

  • Mummy shape minimises airflow to keep the warmth in 
  • 850+ Loft ULTRA-DRY Down provides good insulation and keeps the packed size very small
  • A combination of vertical chest baffles and horizontal lower body baffles that keeps the down in the right places to prevent cold spots
  • Left side 3/4 zip, allows to you open up on those hot nights

We Don't Like

  • Handle with care as the outer and inner shell are lightweight and potentially fragile if you are to rough
  • The drawstring toggle on the neck is a bit small for people with big hands. A slightly larger toggle would improve the ease of use particularly on those cold nights when your hands aren’t working so well
  • A different colour inner wouldn’t show the dirt as much so use a liner to keep the bag clean
  • Not really a year round bag, best for cold conditions
  • No foot box zip limits the versatility of the bag making it to hot in many areas during the warmer months
  • The price! This bag is good value but it isn’t cheap

Best Uses

  • The perfect bag for ultralight hikers who want maximum warmth, minimum weight and that right size in their sleeping bag

Buy One

You can purchase the Sea to Summit Spark SPIII Sleeping Bag Regular from Snowys or from Wildfire Sports

Disclosure:  We may earn a small commission, at no additional expense to you, if you click through and make a purchase. Please note that our affiliations do not influence, in any way, the independence of our reviews. If we don’t like a product, you’ll hear about it from us!

If you have used the Sea to Summit Spark SPIII Sleeping Bag Regular or if you have questions, we’d like to hear from you. Post your comment or questions below


AUD $799.00 RRP. Keep an eye out for the regular sales that occur and you may get a great deal

Other Versions

Sea to Summit Spark SPIII Sleeping Bag

Sea to Summit Spark SPIII Sleeping Bag temperature ratings. This bag will suit the ‘average female’ down to -2° and the ‘average male’ down to -8° Celcius

1 litre water bottle up against the sleeping bag in its compression bag

Neck and zip baffles

Translucent inner shell

Translucent outer shell

Close up of 3/4 zip and zip baffle

Tim inside the Sea to Summit Spark SPIII Sleeping Bag

Storage bag


This review was done with product provided by Sea to Summit for testing

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