Review – Ultralight Sleeping System

Submitted by Thorsten on 27th May 2020

The pandemic has, unfortunately, put a dent in our Polar ambitions for this year, but the COVID situation in Austria has luckily improved enough to allow hiking and trekking trips again. As I’m gearing up for a busy hiking summer at home, I tested a new ultralight sleeping setup made for those warm summer nights to come. It is exceptionally light, weighing only 655g, but is it comfortable, too?


As with any system, the sleeping mat is at the core of it. I’m using the Thermarest NeoAir Uberlite Small.

  • Length: 119cm
  • Weight: 144g (including the sack, weighed by me)
  • R-Value: 2.3

As you can tell from the dimensions already, this sleeping mat is not big enough to support my whole body, but only my core. The idea is, that by keeping the core warm, the legs don’t require the same degree of insulation. To provide a little bit of protection from the cold for the legs, I’m putting down my empty backpack at the foot of the sleeping mat. The contents of my backpack go into my rain cover.

The sleeping bag is the Sea2Summit Spark Sp0, an exceptionally light down sleeping bag.

  • Weight: 251g (including the sack, weighed by me)
  • Rating: 14°C comfort / 10°C limit

I’ve been using this sleeping bag for sleeping indoors in cabins already, but in theory, it should be good to sleep outdoors in warm nights as well. It is incredibly light, weighing less than your average bivy bag.

The sleeping bag and mattress go inside a bivy bag. I’m using the MSR e-Bivy.

  • Weight: 260g* (including the sack, weighed by me)
  • Length: 224cm

* newer version is listed at 200g

I’m using a bivy bag for very basic weather protection. My bivy bag is very lightweight, classified as an emergency bivy. But since this setup is for warm summer nights, I figure it will do. It probably won’t withstand heavy rain showers, but should be enough to keep me dry during a drizzle. The bivy bag is roomy enough to stow some gear in addition to your sleeping setup, so you can put your boots or a stuff sack with electronics inside it, too.

As you’d expect from such a light setup, it has an exceptionally small pack-size too. Here’s a picture of the components with my spoon for scale.


I gave this system a go during my trek in the Reichraminger Hintergebirge at the end of May. The weather forecast was around 10°C for the night, cloudy, but no heavy rain, which is about the temperature limit I expected to get a comfortable sleep in with that system. I do usually sleep in merino underwear and can put on more clothes when the temperatures drop, so theoretically, this could work for colder nights as well. Keep in mind that sleeping bag comfort is very much subjective and you will have to find what temperature range works for you.

Right from the start, I was impressed by how warm the Thermarest Uberlite feels. The difference between my core on the mattress and my feet was noticeable, but luckily my feet got enough insulation from just the sleeping bag and backpack to not freeze. The Spark Sp0 did its job as well, and after about half an hour, I actually began to sweat, so I had to work my upper torso out of the bag, which is a bit fiddly with the small 50cm zip. After regulating the temperature, I quickly fell asleep.

I wish the next sentence in this review were “The next morning I woke up refreshed…”, but that’s not how it turned out to be. Instead, I quickly discovered some limitations of the setup I had picked. After about an hour, I woke up a bit cold, lying on the floor with the sleeping mat on top of me. It turns out that all the components involved in this setup are not only light but very slippery. The sleeping bag on the smooth sleeping mat on the smooth floor of the bivy bag makes every movement feel like you’re lying on a marble floor covered in oil. I tend to move around a lot when sleeping, which is difficult enough on a full-length sleeping mat, but with the torso-length model, it is downright impossible. Usually, when I turn over at night, I can put my weight on my legs and use that to keep the mattress in place. Doing this with the small Thermarest shoots it out from underneath me instantly.

As the night went on, I kept waking up next to or underneath my mattress, and every time I felt a bit colder than before. To my dismay, I also noticed the mattress losing a significant amount of air in these couple of hours, although I didn’t sleep on top of it all the time. I do not know if it’s due to my notoriously bad luck with airbeds or if it’s a feature of the model, but it is something I replicated at home in my living room after the trip, so it’s not due to temperature changes.

As you can see in the pictures, about half of the air has escaped after a night of leaving the mattress lying in my living room with about 30kg weights on top.

Finally, at about 3 am, I decided I had enough of the test experience and switched to my full-length mattress, so I could recover for the next day’s hiking.

Without that slipping issue, I felt that the system would be good enough for the temperatures I experienced. Unfortunately, my way of sleeping just doesn’t seem to fit it very well. Now, this doesn’t necessarily mean it is unusable. Maybe you just don’t move around as much when you sleep. Or maybe I can find a nice ditch next time that will help keep the mattress underneath my body, where it belongs. All in All, I was still surprised by the comfort provided by this extremely light setup. 

If you are an ultralight purist, looking for the lightest of the light, this setup may be worth considering. For me, adding the additional 200g for a full-length sleeping mat is well worth the gain in comfort, so it’s unlikely I will use this exact setup after all.


  • Good warmth for the weight
  • Extremely light (655g total)
  • Extremely small pack-size


  • My mattress loses a significant amount of air quickly
  • Very slippery, not made for heavy movement at night
Review – Ultralight Sleeping System


Keen hiker and ÖAV trekking and hiking guide, in love with Nansen. Owner of the most walk-averse rescue dog ever. Ice cream lover, kit junkie, runner and mad software genius.