For colder conditions, where you need warmth without excess bulk and weight, the Spark Sp4 Sleeping Bag from Sea to Summit ticks all those boxes and more.
This bag has an expedition mummy bag shape which traps warmth, provides extra space, and also allows for extra layers of clothing. The Spark Sp4 has a comfort temperature rating of -8°C and a lower limit of -15°C so it can be used for expeditions in wintry conditions or climates. This bag has an ultra-light 10D nylon shell and 7D lining which keeps the weight to a minimum. To stop heat loss, the bag has a front neck draft collar and a zipper draft tube and access
For insulation, it’s filled with RDS certified 850 Loft Premium
For maximum warmth when you’re counting every single gram, the Sp4 Sleeping Bag from Sea to Summit is the ultimate sleeping solution.
Some online reviews have suggested the YKK #3 zips get a bit stuck and are hard to use. Have these been improved in rolling changes over the years? is its still a #3? Beyond the spark range, do you have any suggestions for a similar weight bag in this comfort rating?
G'day Jo,
As they are a fine zip we have seen that now and then. Currently, they are still a #3 YKK zip. We have heard recently that Sea to Summit are looking to upgrade the zip to a #5 YKK zip so we should see that change in the coming months!
Besides the Spark & Flame Sleeping Bags, there is the Amplitude Am3 (−8°C), Journey Jo2 (−8 °C) and Altitude At2 (−10 °C). They are a little heavier but do have the #5 zips and a similar comfort rating.
I was looking at buying this sleeping bag and wanted a dry bag compression sack (from sea to summit) to go with it. What size would work with this bag?
G'day Sonya,
The Spark SP4 Sleeping Bag is supplied with a Small Ultra-sil compression stuff sack, so if you're wanting to keep your bag watertight, then the Small Compression Dry Sack will do the trick.
Is it advisable to treat the outer with DWR or similar without compromising breath ability of your bag
G'day Trevor,
I've just had a chat with one of my colleagues who has the women's version of the bag. She reported she's experienced a little bit of condensation, but not much, and she'll just loft it out as soon as she sets up camp the next night and if there is any dampness it soon dissipates. We wouldn't recommend treating the outer shell with DWR.
Does this sleeping bag fully unzip into a quilt? And also does it have a foot zip?
G'day Jason,
Thanks for your enquiry. The Spark SP4 does not come with a foot zip and cannot unzip to create a quilt, I'm sorry to say. Check out the Trek Tk3 and the Explore Ex3 as these bags do offer these features and have similar comfort ratings and fill material.
Are the packed dimensions really this? Packed Dimensions: 44L x 48W x 20H cm
G'day Doug,
At the moment we're getting all this info from Sea to Summit and as we don't actually have the bags yet I can't double check it for you. If it helps at all they're also telling us it comes packed in a 'Small' Ultrasil Compression Sack which measures 40cm x 18cm x 18cm and has a compression range of between 10L and 3.3L.
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