• Weight (long size) 614 grams
  • Recommended Maximum User Height 198 cm
  • Female Comfort Rating 4° Celcius
  • Male Comfort Rating -2° Celcius
  • Cost $649.00

Sea to Summit Spark SPII Sleeping Bag

Sleep Systems


Rating: 8.5 / 10
Weight 1.9 / 2
Value for Money 1.7 / 2
Durability 1.6 / 2
Warmth 1.6 / 2
Versatility 1.7 / 2

Sea to Summit Spark SPII Long Sleeping Bag Review

For a number of years I have been scanning the internet and outdoor magazines for a new ‘go-to’ sleeping bag before having the opportunity to test out the Sea to Summit Spark III Sleeping Bag;  in all honesty that was the way I thought I was going to head.

From 2014-2017 my main sleeping bag was one that coped with -4 degrees Celcius (men’s comfort level) and in just about every overnight hike I did, it was well and truely overkill. In addition that particular bag weighed in at just over 1kg and while its a high quality comfortable bag, it didn’t really pack down that small. So in 2018 I pivoted the other direction and choose a now superseded sleeping bag from Sea to Summit that had a men’s comfort level of 2 degrees Celcius, packed down to almost nothing and weighed in at 720 grams. This lighter weight bag accompanied me on all my overnight hikes up until early 2021 and while it’s a great warm weather bag and suited me down to around -2 degrees Celcius it just didn’t cut it at the sweet spot of around -5 which is what I regularly expect in my local area. After another year of procrastinating and I ended up buying the Sea to Summit Spark II (long version) and here’s why.

My first priority was choosing a bag rated at a men’s comfort rating of around -2 degrees Celsius which I know will comfortably suit me down to -5 degrees Celsius. Having said that, this is a very personal comfort level. I’ve worked outdoors in some very cold conditions for most of my life and I tend to be a hot sleeper. If you are a cold sleeper you are best sticking to the minimum rated warmth or even going for a warmer bag. I have used this bag on some very cold nights and have been very comfortable. In the images below which I took for this review, the daytime temperature was under 10 degrees Celcius and I quickly found myself overheating even in the short time it took me to take the shots.

The Sea to Summit Spark range are high-end bags no matter what model you go for and are best described as technical bags. By technical I mean that features deemed unnecessary have been stripped out or minimised all in the aim of providing the lightest, warmest, most compact-able bag possible.

You don’t get a zippered toe box, you don’t get a full length zip and you don’t get an internal security pocket but all this contributes to almost non-existent weight. The Spark II (long) bag I purchased in its stuff sack weighs just 614 grams compared to the 560 grams quoted for the Sea to summit website. Even with this slight discrepancy, this is by far the lightest sleeping bag I have ever owned.

A big contributor to this minimal weight comes from the use of 850+ loft Goose down. In plain English what this means is that gram for gram when you try to achieve the same warmth from a 650 or 750 loft bag, you do so with the use of more down which increases the weight and bulk but also reduces the price. Sea to Summit use what they call ULTRA-DRY Down™ which means it is moisture repellant, protecting the down from external moisture and condensation. While we are on the subject of down, Sea to Summit use the ‘Responsible Down Standard’ in their bags which is a polite way of saying that the down isn’t plucked from live animals but instead taken from birds used in the meat industry and that also considers the welfare of the animals while still alive. Each bag comes with its own certificate (see image below). The other big benefit with using 850+ loft down is that the bag packs down very, very small.

Being a high quality bag the Sea to Summit Spark II also has all the relevant baffles including along the zip and the hood to keep you toasty and warm. The 1/2 zip is two way so it allows you to open the zip from the mid section of the bag to allow air to flow into the bag to cool you down if need be.

Construction-wise the Spark II like most of the Spark range (with the exception of the Spark 0) uses a combination of vertical and horizontal baffles that help keep the down where it belongs. I also opted for the ‘long’ version as I’m just over the recommended height for the ‘regular’ bag. I know I can fit into the regular but its a bit of a jammed feeling. The additional bulk and weight is marginal so that really didn’t factor into my decision and while I purchased this bag purely based on the length, I hadn’t fully realised that the long bag is also slightly broader overall which is an added bonus if you have never used a mummy bag before. Speaking of mummy bags, they are a snug fitting bag that minimise air movement inside the bag which means that it heats up quicker than a rectangular or tapered bag and maintains that heat better as well, but can be a bit claustrophobic if you aren’t used to it. The heavier weight Sea to Summit Spark III bag was the first mummy bag I had ever used and even with my giant feet, I still had room to move and that was in the regular size.

One less obvious feature on the new range of Spark bags is a series of small innocuous looking loops that are designed to connect with the Sea to Summit quilt range like the Cinder. This turns this bag into almost a layered sleeping bag for when it gets really cold.

Now for the negatives and while they exist none of them were deal breakers for me. I’m a strong believer that there is no such thing as a perfect product and this includes sleeping bags. The first negative for me is purely cosmetic with the internal bag colour being bright yellow and while the bag looks good it has the potential to mark if you don’t use a sleeping bags liner. I do, so not a problem.`

The next negative is the lightweight material used. While this helps to minimise the bag weight you do need to handle it with care. 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 to loan to a novice hiker friend or use as a hire bag. I’m a big guy and can be rough on gear but I’ve just gotten into the habit of not rushing when I get into the bag.

The 1/2 zip which helps keep you warm and minimise airflow in the cooler months also means that trying to use this bag in mid summer isn’t going to work for you – you will quickly overheat. This is not a summertime bag!

Like most sleeping bags the Spark II comes with a loose fit storage bag as well as a tiny compression sack. The storage sack on this bag takes upon much less room in my storage cupboard mainly due to the 845+ loft down but when you pack this bag into its compression sack, its a bit fiddly and does take me longer to get it packed as the compression sack is exactly the right size with no room for forgiveness.

One very minor negative is that as someone with big hands, the toggle on the hood is a bit small and while I am used to it a larger toggle would have been nice.

Last but not least as a high-end bag the Spark II is not cheap with a RRP of around $599AUD (regular) or $649AUD (long) putting it in the higher price range and more than what many but the keenest hiker is likely to spend on a bag. However when you compare this particular model with more highly featured bags such as the Sea to Summit Ascent II then it doesn’t look that bad. Rather than providing a feature rich bag like the Ascent, the Spark II focuses on weight and size instead so this is going to be where you make your decision.

Usually at this stage I ask the question ‘Would I buy it?’ but in this case I already did. The Spark range of bags is aimed at those hikers who travel fast and light and value this criteria first and foremost. Given the price of this bag, it’s not going to be for everyone and it isn’t a summertime bag. It is however my new bag of choice for much of the year and one that I can see myself getting many years use out of. 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 in the warmth. The long size provides some extra width as well as the extra length for those who need it 
  • 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 keep the down in the right places to prevent cold spots
  • Left side 1/2 zip, allows to you open up on those hot nights
  • Very lightweight, very compact, toasty warm without being hot!
  • A good set of baffles to minimise cold air entering the bag
  • Designed to work with the Sea top Summit range of quilts to create a layering system

We Don't Like

  • Handle with care as the outer and inner shell are lightweight and potentially fragile if you are too 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
  • Best for cold conditions, not so great for hot weather
  • No foot box zip. In this bag it helps retain the heat and minimises the weight but limits the versatility in the hot weather

Best Uses

  • The perfect bag for ultralight hikers who want maximum warmth, minimum weight and that tiny size when packed which doesn’t take up space in your pack

Buy One

You can purchase the Sea to Summit Spark SPII 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 SPII Sleeping Bag Regular or if you have questions, we’d like to hear from you. Post your comment or questions below


AUD $649 RRP. Keep an eye out for the regular sales that occur and you may get a great deal

Other Versions

The above are men’s temperatures ratings

Sea to Summit Spark SPII Sleeping Bag

SparkII Size chart. The long bag is also a bit broader as well. I’m a large guy and can fit into the regular size bag but its just not long enough

Sea to Summit Spark SPII Sleeping Bag temperature ratings. This bag will suit the ‘average female’ down to 4° and the ‘average male’ down to -2° Celcius. For me this bag keeps me happy at -5° Celcius

Bag test report

Bag in storage sack. Its actually smaller than it looks

Stuffing the bag into the stuff sack

Spark II in stuff sack

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

Bag unpacked and ready to go

Hood baffle

Hood toggle, a bit small if you have big fingers

1/2 zip open

Zip baffles

Inside of the Sea to Summit Spark 2. The inner shell look ‘dirty’ because its almost translucent allowing you to see the down through the material

Tim in the Spark II with hood loose

Tim in the Spark II with the drawstring pulled tight. I had plenty of space and didn’t feel constricted even though this is a ‘mummy bag’

Tim inside the Spark II

Toe box Spark II. This toe box isn’t as small as some mummy bags particaluiry on the ‘long’ bag which is more generous


This review was done with product purchased by Australian Hiker

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