Sea To Summit Ether Light XT Extreme sleeping mat review: a ridiculously comfy yet packable camping bed

Bring some luxury to your camping experience with the epic Sea To Summit Ether Light XT Extreme sleeping mat

Sea To Summit Ether Light XT Extreme
(Image credit: Mark Mayne)
T3 Verdict

The Sea To Summit Ether Light XT Extreme is a portable mattress that puts most competitors to shame. This offers serious comfort at only a small weight penalty.

Reasons to buy
  • +

    Really, really warm

  • +

    Really, really thick and comfortable

  • +

    Pretty lightweight

Reasons to avoid
  • -

    There are lighter summer options

 The Sea To Summit Ether Light XT Extreme sits near the top of the Sea To Summit range, a juiced-up version of the classic Ether Light XT sleeping mat, designed for those who want big comfort or big insulation at a slight weight penalty. The super-thick, warm design means it could sit amongst the best camping mats or the best camping beds. We put it to the test to see how it performs in practice. Read on for our full Sea To Summit Ether Light XT sleeping mat review. 

Sea To Summit Ether Light XT Extreme: design and build

The Sea To Summit Ether Light XT Extreme is an air mattress with a difference - or a few differences to be exact. At 10cm thick, inflated, it’s far thinner than a standard air mattress, and much thicker than a lightweight mat. Although there are plenty of similar-looking air pouch-style mats on the market, this stands out due to the Air Sprung Cell design that allows each cell to deform to your body shape. This extra-thick iteration uses multiple TPU loops to connect the top and bottom layers of fabric to the spot welded Air Sprung Cell chambers inside the mat, which allows a greater thickness of mat, and thus better comfort. 

The Sea To Summit Ether Light XT Extreme is available in four configurations, regular (as tested here), long, and then two rectangular versions in similar lengths. The rectangular versions offer slightly more comfort at the expense of weight and bulk, so it’s worth considering which fit your usage most closely. 

Sea To Summit Ether Light XT Extreme review

(Image credit: Mark Mayne)

Deflated the Sea To Summit Ether Light XT Extreme in regular is a fair size, about the bulk of a 500g bag of pasta (a quoted 11 x 24cm), but not too bulky that it’s not portable. The mat is aimed mainly at delivering maximum comfort and insulation, whether for car-campers seeking a lightweight luxury mattress, or winter hikers who need the massive R-value, the spec is the same – an R-value of 6.2, like sleeping on a good sofa. 

The valve is particularly well-designed, a rubberised tab system (inflate and deflate) allowing you to either select the one-way inflate valve or the quick ‘deflate’ open hole. This allows the stuff sack pump to work fairly well, a triumph of valve design over physics. The one-way valve setting has an orange button in the centre for fine adjustments too – helpful when dealing with big daytime/nighttime temperature changes. 

Sea To Summit Ether Light XT Extreme

(Image credit: Mark Mayne)

Ether Light XT Extreme review: performance

 That huge R-value seems pretty realistic when you’re perched on the enormous depth of this mat, and as you settle down to snooze it’s apparent that the huge airspace is reflecting heat back up in serious volume. Side sleepers will be pleased too, as the depth is easily able to cope with position changes and non-flat sleeping choices. Overall it is enormously comfortable, and very warm indeed, both as billed.

Sea To Summit Ether Light XT Extreme

(Image credit: Mark Mayne)

As mentioned, the stuff sack inflation scheme does work, albeit a little slowly, taking around eight squishes of the sack to fully inflate the mattress. You can of course just cheat and blow it up, but this puts moisture into the mat that’s not only bad for the insulation values as you sleep, but also not ideal for longevity either. One interesting issue we found in testing is that the mattress is so thick and deep it can feel unstable and insecure at times, like it’s overly top-heavy, although that’s entirely dependent on your sleeping style and flatness of your campsite.

The 30/40D Nylon face fabric is a little ‘crinkly’ in use. Not as bad as some, but not silent either, something to bear in mind if you’re sharing a tent.

Sea To Summit Ether Light XT Extreme sleeping mat review

(Image credit: Mark Mayne)

Sea To Summit Ether Light XT Extreme: verdict

Really there’s little for Sea To Summit to have got wrong in the Ether Light XT Extreme, given that it’s a beefed up version of an existing popular model, and that is indeed the case. The aim is to deliver warmth and comfort, and you’ll get lots of that here. 

There are lighter, slimmer, more packable camping mats around, but they’re colder and less comfortable, so you takes yer choice, as the old saying goes. If you’re really gram-counting in summer or autumn conditions you could save weight with a lighter mat/mattress option, but in winter there’s not many camping beds or mats out there with this much insulation firepower, potentially letting you run a lighter sleeping bag as a result.

Overall, this is dangerously close to the ideal camping bed for all occasions, from car camping with the family to summer hikes, winter overnight adventures to base camp comfort, this only compromises slightly at the very extremes. 

Mark Mayne
Mark Mayne

Mark Mayne has been covering tech, gadgets and outdoor innovation for longer than he can remember. A keen climber, mountaineer and scuba diver, he is also a dedicated weather enthusiast and flapjack consumption expert.