Sea to Summit Ether Light XR Insulated ASC Review 2025
Last Updated: February 11, 2025
By Jaeger Shaw
Full Analysis of the 2025 Sea to Summit Ether Light XR
Warmer, Lighter, Quieter, and More Packable than Original XT Version
The new-for-2025 Sea to Summit Ether Light XR Insulated ASC Sleeping Pad is warmer, lighter, quieter, and packs down smaller than its predecessor, all without a price bump. The combination of its S-tier comfort and highly competitive R-value-to-weight-ratio makes it an immediate contender for best overall sleeping pad on the market. This review cover features stats, pros, cons, and comparisons to its chief competitors, Nemo Tensor and Therm-a-Rest NeoAir, as well as its previous version. And in case you were wondering, ASC stands for Air Sprung Cells, Sea to Summit’s proprietary internal pad structure.
Specs for Ether Light XR, Regular Mummy
- Price: $199
- Weight: 16.6 oz
- R-Value: 4.1 | R-Value/Weight: .25
- Thickness: 3.9”
- Fabric: 30/40d Nylon face
- Sizes: Regular Mummy (72×21.2″), Large Mummy 77×25.2″, Short Mummy (66×22.7″), Regular Wide (72 x 25.2), Large (77 x25.2)
- Marketplace Comps: Therm-a-Rest NeoAir XLite, NEMO Tensor All-Season, Big Agnes Zoom UL
- Pros: Very comfy sleeping surface. Warm. Quiet. Pillow lock feature. Durable fabric. Perimeter bumpers. A bit thicker and wider than average.
- Cons: Light-not-ultralight. Competes with warmer/lighter options.
Editor’s note: At time of publication, the Sea To Summit Ether Light XR was only just released, and our testing experience is limited. We will update this review should any new information reveal itself after a full season of backcountry use.
Compare to more great options in our guide to the best sleeping pads for backpacking, as well as winter sleeping pads and double sleeping pads.
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Design Overview: Construction, Materials, Features
What most separates Sea to Summit Ether Light XR Insulated ASC Sleeping Pad from its competitors are the Air Sprung Cells. ASC is the acronym from its namesake, and STS’s proprietary internal workings of the Ether Light pad series. Think of them like box baffles on a down garment reinforced with TPU columns that provide stability and structure that prevents sinkage, as well as a top surface comprised of peaks and valleys that do an excellent job of dispersing shoulder/hip pressure for side sleepers.
What we’ve learned with sleeping pad testing is that the deeper the surface valleys, the comfier the pad will be for side sleepers. Thanks to all of the above, we find it to be very comfortable, and one of the comfiest in its weight class. Of course heavier bulkier pads can be comfier, the Therm-a-Rest NeoLoft is much comfier, but few pads weighing ~1 lb can beat the Sea to Summit Ether Light XR.
The pad is 3.9″ (10cm) thick at the enlarged edges, which helps keep sleepers centers, and closer to 3.5″ for the majority of the non-edge surface. This thickness is sufficient to block out nearly all roots and lump, and equivalent to other premium price point sleeping pads.
Ether Light XR has an R-Value of 4.1 thanks to its ThermalCore insulation, a multi-layered polyethylene film. At present, the R-Value range sweet spot for three season use is 4-5, so it definitely checks the warm-enough box, and should perform well for quilt users without any sleeping bag insulation underneath.
The exterior of the pad is made with a 30/40d nylon face fabric laminated to the TPU body. This is at least as durable as all of its core competitors.
Closing it out with features, we note the user-friendly and secure valve, which can be used for micro adjustments to the inflation level, and deflates quickly when packing up. It also comes with a repair kit featuring multiple patches, as well as components for the Pillow Lock which are stick on hook-and-loop tabs that keep the underside of any STS pillow in place. It has a large and functional storage bag pump sack combo unit that weighs 1.9 oz.
FAQ Sea to Summit Ether Light XR
Is it comfy for side sleepers?
Yes! The Sea to Summit Ether Light XR Insulated ASC Sleeping Pad is a great option for side sleepers, and the deep surface ridges/valleys of its Air Sprung Cells do a phenomenal job of dispersing shoulder and hip pressure for side sleepers. We find it is comfier than competing options like Therm-a-Rest NeoAir XLite NXT, and NEMO Tensor All-Season. If you simply want the comfiest option possible, choose the Therm-a-Rest NeoLoft.
Is it warm enough for quilt users and three season use?
Yes, at R-4.1, it is warm enough for quilt users, and for use in temps down to freezing. If you are expecting cold weather and temps below freezing, we recommend the “Pro Version“, which is an otherwise identical winterized Ether Light with an R-Value of 7.4.
How durable is it?
In context of the marketplace, it’s 30/40d face fabric is thicker and at least hypothetically more abrasion/puncture resistant than others. STS also claims that they’ve increased weld strength. All said and done, this feels like a well made, durable sleeping pad that’s likely to hold up well in the backcountry. That being said, you should still practice care with all inflatable sleeping pads and leave them in the tent.
Who should choose it?
The Sea to Summit Ether Light XR Insulated ASC sleeping pad is a great option for all backpackers, from beginner to expert level. It is user friendly, comfy, warm, and light. Even hardcore ultralight backpackers should consider it given that it is only 3-4 oz heavier than other best-in-class options from Therm-a-Rest and NEMO.
Should you upgrade from old XT to new XR?
More on this below, but in summary, the XR is a strict upgrade over the old XT version. But if you have a functional XT and it still works for you, we’d suggest keeping it until a replacement is required. If you found the old XT to bee too noisy or not warm enough, than upgrading may be worthwhile.
Which size should you choose?
This is a very subjective question and impossible to answer in black and white. But we always suggest starting with a regular sized mummy pad to establish a baseline and maximize weight savings. If that’s not big enough for you, start sizing up to long/wide/rectangle as needed.
2025 Sea to Summit Ether Light XR vs XT (2020 version)
Comparing the new-for-2025 Sea to Summit Ether Light XR vs it’s predecessor the XT is a slam dunk win for the XR. The new version is much warmer, much quieter, slightly lighter weight, more durable, and packs down smaller, all while costing the exact same amount of money. Basically, the new version is strictly superior. As far as we can tell, the only advantages to the old version is that it’s now on clearance sale. Technically the thickness of XT is listed at 4.0 vs 3.9 for the XR, and size regular XR is .3″ narrower than XT, but that could come down to something as silly as measurement variance.
Advantages of new XR over old XT
- Perceptible much quieter to roll around on
- 0.7 oz lighter weight (regular mummy)
- New insulation consists of TRM layers packs down smaller
- 0.9 increased R-Value (R-4.1 up from R-3.2)
- increased weld strength improves durability.
Similarities of both new XR and old XT
- Same $ MSRP
- Same thickness
- Same perimeter bumpers to center the sleeper
- Same comfortable Air Sprung Cell surface
- Same size and shape
- Same size range
- Same valve
- Same pump sack
- Same pillow lock
- Same face fabric
At time of publication, the previous version is on sale at 25-50% off at STS and REI.
Sea to Summit Ether Light XR vs Therm-a-Rest NeoAir XLite NXT
Therm-a-Rest NeoAir XLite NXT is the juggernaut in the lightweight inflatable sleeping pad niche, but is it better than the Sea to Summit Ether Light XR? In some ways yes, on other ways no. The short answer is that Ether Light XR is comfier, but Therm-a-Rest NeoAir XLite NXT is lighter and warmer. For starts, we compare the regular sized mummy for each.
Advantages of Sea to Summit Ether Light XR
- Comfier surface with deeper valleys, especially for side sleepers
- $11 less expensive (regular mummy)
- Perimeter bumper keeps sleepers centered
- Pillow lock feature, if desired
- 1.2″ wider (regular mummy)
Advantages of Therm-a-Rest NeoAir XLite NXT
- Notably lighter weight, by 3.6 (regular mummy)
- Slightly warmer, 0.4 higher R-value
- Multiple seasons of proven durability
- Packs down smaller
- Made in USA
Similarities of Both
- 3.5″ thick main area (3.9″ thick measurement of Ether Light XR refers to perimeter bumper)
- Top tier performance option for backpackers
- Lightweight
- Warm
- Thick
- Durable
- Thermal film-based insulation
- Includes repair kit and pump sack
Sea to Summit Ether Light XR vs NEMO Tensor All-Season
Prior to the release of Sea to Summit Ether Light XR, the NEMO Tensor All-Season was our favorite sleeping pad, but now it’s too close to call. Both have some advantages and disadvantages compared to the other as highlighted below. Which to choose comes down to your priorities:
Advantages of Sea to Summit Ether Light XR
- Slightly comfier surface with deeper valleys
- 1.2″ wider (regular mummy)
- Perimeter bumpers
Advantages of NEMO Tensor All-Season
- Much warmer, R-Value is 1.3 higher (5.4 vs 4.1)
- Lighter weight by 2.5 oz (regular mummy)
- Bluesign approved fabrics are more sustainable
Similarities of Both
- 3.5″ thick main area (3.9″ thick measurement of Ether Light XR refers to perimeter bumper)
- Same price
- Top tier performance option for backpackers
- Lightweight
- Warm
- Durable
- Thermal film-based insulation
- Includes repair kit and pump sack
Sea to Summit Ether Light XR Review Conclusion
The 2025 Sea to Summit Ether Light XR Insulated ASC is a big upgrade over its predecessor, and an obvious contender for best overall backpacking sleeping pad, even compared to top pads like NEMO Tensor All-Season and Therm-a-Rest NeoAir XLite NXT. Both of which are lighter and warmer, but neither of which are comfier. Ether Light XR’s strong marketplace positioning is thanks to top of the line comfort, great stats, and a user-friendly design and feature set. Happy camping!
