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Ether Light XT Extreme Insulated Air Sleeping Mat

Cleverly constructed comfort for the coldest conditions

$199.00 – $229.00

Sleeping Bag Temperature Ratings Explained

The EN Rating scale is a scientific test to determine the warmth of a sleeping bag. The test produces a Lower rating (for male sleepers) and a Comfort rating (for female sleepers). Both are listed in the features table on the product page.

A unisex sleeping bag with a Lower limit of 14ºF means a man should be comfortable down to air temperatures of 14ºF. The same bag will also have a Comfort limit, in the realm of 27°F, so a woman would be comfortable down to an air temperature of 27ºF. These ratings require a sleeping mat with an R-Value appropriate for expected ground temperatures – without this, the sleeping bag itself is unlikely to keep the sleeper warm enough.

A variety of factors impact sleeping bag warmth - the above temperatures are merely guidelines, not guarantees. It’s important to think of a sleeping bag, an appropriately insulating sleeping pad and a liner as a sleep system. For example - if you plan on sleeping in nighttime air temperatures of 27ºF / -3°C, choose a bag with a gender-appropriate rating of 23°F / -5°C, plus a sleeping mat with an R-Value of 2.5 to 3, and consider a Reactor thermal liner.



The Ether Light XT Extreme is extra thick and exceptionally warm. The XT Air Sprung Cells provide 4" of stability and comfort, while dual-density layers of THERMOLITE® insulation prevent convective heat loss and internal air movement. The result: true four-season performance.

Our blog post "Which Sleeping Mat to Choose" has some helpful tips on picking the perfect air mat (or reasons why you might prefer a Self-Inflating sleeping mat).

Technical Features

Thermolite® HL-1

Thermolite® HL-1 is part of the family of Thermolite® materials used in Sea to Summit sleeping bags, sleeping bag liners and sleeping mats. HL-1 high loft insulation is a fiberfill constructed with a unique 3D crimp of hollow-core and solid fibers, which provides excellent lightweight warmth with superior durability. The Thermolite insulation lofts up inside the Air Sprung Cells™ of our sleeping mats to prevent convective heat loss from your warm body to the cold ground.

Integrated AirStream™

The Airstream™ Pumpsack is Sea to Summit's big volume mattress pump which we've now integrated into the stuff sack of every Air Sprung Cell™ mat. The clever design opens at one end to stow the air mat and the other end unfolds to become the built-in pump.

The Airstream™ Pumpsack can be inflated with a single breath and takes just two or three cycles to fill our mats. Not only is it faster than inflation by mouth, but there is minimal breath condensation entering the mat and it eliminates dizziness from blowing the mat up directly by mouth.

The Airstream™ Pumpsack is also compatible with Sea to Summit's smaller multifunction valve, which is now featured on the updated Aeros pillow range, along with the Air Seats.



To ensure that you will be warm when you sleep (especially when the ground is colder), it is essential to know how well your sleeping mat resists heat loss into the ground. This resistance is known as an R-Value.


A laboratory-tested R-Value is the only way to measure resistance to heat loss. Sea to Summit has always provided independent lab-tested R-Values for its sleeping mats.


Since January 2020 we have used the industry standard ASTM F3340-18 test to provide R-Values for our mats.


There are other factors which will determine how well a sleeping mat will insulate; but the standardized ASTM R-Value test means that you can compare resistance to heat loss in sleeping pads across different brands.

Ether Light XT Air Sprung Cells™

Air Sprung Cells™ are the core technology used in Sea to Summit Air Mats and are the reason you will sleep more comfortably on a Sea to Summit mat than on a conventional air pad. Inspired by the springs of a modern pocket sprung mattress, dozens of interconnected chambers (called Air Sprung Cells™) perfectly support your weight and conform to your body contours.

The Ether Light range uses loops of TPU material to connect the top and bottom welds. This produces a thicker cell to give you a plush sleeping experience without compromising on Sea to Summit's Air Sprung Cell comfort.

Tech Specs

Product Details

Best Use
Cold Weather Backpacking
Comes With
Stuff sack w/ integrated pump, repair kit & Pillow Lock
Durable 30D/40D nylon
Season Rating
4 Season
Anti-microbial liquid-extruded TPU lamination to reduce delamination
4 in / 10 cm
ether-light-xt-extreme-insulated-air-sleeping-mat-regular.svg ether-light-xt-extreme-insulated-air-sleeping-mat-large.svg ether-light-xt-extreme-insulated-air-sleeping-mat-rec-reg-wide.svg ether-light-xt-extreme-insulated-air-sleeping-mat-rec-large.svg
72 x 21.7in / 183 x 55cm
6.9 x 9.4 in / 17.5 x 24cm
2.2 oz / 62 g
4 in / 10 cm
25.4oz / 720g
78 x 25.2 in / 198 x 64cm
7.3 x 11 in / 18.5 x 28cm
2.3 oz / 65 g
4 in / 10 cm
33.5oz / 950g
72.1 x 25.2 in / 183 x 64cm
7.3 x 11in / 18.5 x 28cm
2.3 oz / 65 g
4 in / 10 cm
33.5oz / 950g
79.1 x 25.2 in / 201 x 64cm
7.3 x 11 in / 18.5 x 28cm
2.3 oz / 65 g
4 in / 10 cm
37oz / 1050g


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