Sea to Summit Ether Light XT Extreme Sleeping Pad Review

JUMP TO: SPECS  /  PROS & CONS  /  HOW IT PERFORMED  /  FEATURES  /  ACCESSORIES  /  SUMMARY

Author: Sam Brilleman

The Sea to Summit Ether Light XT Extreme Sleeping Pad is a highly cushioned, highly insulated sleeping pad made for cold-weather backcountry adventures. With double the insulation value of its three-season sibling, the Ether Light XT Insulated Sleeping Pad, the XT Extreme is designed to provide winter-worthy performance in a relatively lightweight package.

Although the Ether Light XT Extreme is heavier and bulkier than some competing ultralight winter sleeping pads, it is durable, well designed, and provides impressive comfort and protection from snowy, frozen ground. If you backpack in winter conditions, or just highly value your beauty sleep in the backcountry, this pad deserves a closer look.

SPECS

SIZE TESTED: Regular

WEIGHT: 25 oz / 720 g

DIMENSIONS (L x W): 72 x 21.5 in / 183 x 55 cm

PACKED SIZE: 6.9 x 9.4 in / 17.5 x 24 cm

SEASON RATING: 4 Season

R-VALUE: 6.2

PROS

  • Comfortable: 4 inches of cushioned and supportive padding

  • Highly Insulated: Its 6.2 R-value among the best at the price and weight

  • Innovative valve system make inflating/deflating quick and easy

  • Cheaper than comparable sleeping pads

CONS

  • Heavier than some winter sleeping pads

  • A large puncture can compromise its insulating properties: risky for winter backpacking

  • Large packed size

HOW IT PERFORMED

COMFORT: With Sea to Summit’s signature “Air Sprung Cell” design and a luxurious 4-inch thickness, the Ether Light XT Extreme is extremely comfortable. There is no risk of your shoulders, hips, or feet bottoming out on cold, hard winter ground—side sleepers rejoice!

The forgiving, mattress-like matrix of air pockets conforms to the body better than pads with horizontal baffles—which tend to feel like hard, air-filled boards—or vertical baffles, where the channels between baffles can make for an awkward sleeping experience.

At 21.5 inches wide, the regular sized, tapered pad is approx. 1.5 inches wider than comparable pads like the Thermarest NeoAir XTherm or Nemo Tensor Alpine Ultralight. You don’t feel like you are constantly at risk of tipping off, as you might on slimmer sleeping pads.

The pad’s 30-denier and 40-denier nylon surface is not exactly quiet, but it should not be a concern unless you (or your tent partner) are an especially light sleeper. It is definitely not as disruptive as the ultralight, but infamously loud, NeoAir XTherm.

 

At 4 inches, The Sea to Summit Ether Light XT Extreme is quite a bit thicker than most comparable pads, including those in the Thermarest Neo Air range (2.5 inches).

 

INSULATION: The insulating abilities of sleeping pads are measured by R-values, which indicate how well a pad prevents heat loss from your body to the cold ground beneath you. R-values above 4.5 to 5 are capable of handling frozen ground and below freezing temperatures. With an R-value of 6.2, the Ether Light XT Extreme is solidly in winter performance territory.

In our tests, the pad provided excellent warmth through brisk overnight temperatures. Depending on your shelter and sleeping bag, it could take temperatures as low as -10 degrees F before you even begin approaching the performance limits of the XT Extreme’s insulation.

EASE OF USE: The pad employs Sea to Summit’s well designed valve system. Two integrated ports make inflating and deflating the pad quick and easy. The one-way inflation valve has a button to release air as needed. Its Airstream Pump stuff sack (2.2 oz.) also doubles as a pump sack that is surprisingly effective. You can fully inflate the pad in about a minute. The large open hole deflating valve makes packing up and getting it back into the stuff sack even quicker.

 
 

WEIGHT: The Ether Light XT Extreme is relatively light for a winter sleeping pad, but it is not the lightest. At 25 oz., it is downright heavy compared to the NeoAir XTherm’s 15 oz.

But the NeoAir XTherm aside, there are few other backpacking pads that match this R-value without being considerably heavier. And the Ether Light XT Extreme outmatches the NeoAir XTherm by being far more comfortable at a slightly lower price point. Unless ultralight gear is your non-negotiable top priority, the comfort and relatively quiet materials are worth the extra 10 oz.

DURABILITY: 30-denier and 40-denier nylon fabric are more durable than some commonly used sleeping pad materials. A liquid extruded lamination and anti-microbial treatment add additional protection and work to prevent internal mold growth.

As with any air sleeping pad, punctures are the primary threat to the Ether Light XT Extreme’s durability. A puncture would eliminate most insulation between you and the ground, which could be catastrophic when winter camping in the backcountry. The tent does come with a patch kit that will serviceably repair smaller rips and punctures. Camping with a groundsheet or tent footprint can minimize puncture risk and extend the pad’s lifespan.

Layering a closed-cell pad underneath can also offer protection and back up insulation. Many winter backpackers take this approach, but it will add significant weight and bulk to your pack.

 

At 21.5 inches wide for the regular size, there is also slightly more width than many otherwise comparable pads that are 20 inches wide.

 

NOTABLE FEATURES

PILLOW LOCK: Sea to Summit sleeping pads have a unique Pillow Lock feature. Compatible pillows can secure to the pad via self-adhesive hook-and-loop patches, preventing slipping and minimizing readjustments to your sleep system through the night.

INTEGRATED AIRSTREAM STUFF SACK/PUMP SACK: The Airstream Pump Sack makes pad inflation effortless and adds next to no additional weight. Built into the sleeping pad’s stuff sack is a connector valve that secures to the pad. Inflate the sack with a single breath, then compress the air into the pad. It only takes five or six breaths to fully inflate.

By using the Airstream Sack, you avoid blowing air directly into the pad, minimizing the risk of condensation and mold buildup within the pad’s interior.

THERMOLITE INSULATION: The Ether Light XT Extreme uses Thermolite HL-1 insulation. Thermolite is a high loft blend of down-like hollow-core and solid polyester fibers, combining warmth and durability for cold and wet conditions.

SIZING: The Ether Light XT Extreme is available in four sizes: regular (25 oz.), large (34 oz.), rectangular regular wide (34 oz.), and rectangular large (37 oz.). The regular and the large taper at the feet, cutting some weight and bulk. The rectangular variations run heavier but provide more protection for those who like to stretch their legs out. Regular sizes will comfortably fit those shorter than 5’11. Go for a large if you are 6’ or taller.

 

The provided stuff sack doubles as a pump sack — and it is pretty good at doing it’s job — it creates a solid seal with the inflation valve, seems robust, and captures and compresses air relatively efficiently.

 

OPTIONAL ACCESSORIES

PILLOWS: Many ultralight backpackers consider pillows an extravagance, but their weight-to-value ratio often makes them a worthy one, especially with Sea to Summit’s Pillow Lock feature. For just a couple of ounces, the Aeros Ultralight Pillow provides comfort you will be thankful for on cold winter nights.

PILLOW CASE: If you have an Aeros pillow from pre-2019, it will not be Pillow Lock compatible with the Ether Light XT Extreme. But you can make it so with an Aeros Pillow Case. Pillow cases have the added benefit of being easily hand or machine-washed.

DRY SACKS: Keeping your sleep system dry can be a matter of life and death when winter backpacking. It is worth investing in a few lightweight dry sacks to protect your gear and clothing in snowy or rainy winter weather conditions.

 

The Ether Light XT Extreme comes with self-adhesive patches that essentially form their so-called “Pillow Lock System” — one side of the patch sticks to the pad, the other side “sticks” (kinda like velcro) to the fabric of S2S pillows made from 2019 onwards.

 

SUMMARY

The Sea to Summit Ether Light XT Extreme stands out as one of the best winter backpacking sleeping pads available. While not the lightest or most packable winter pad, it is no slouch, either. And the pad overdelivers on comfort, usability, and warmth—all at a competitive price point.

Anyone testing the extremes of winter conditions and pack weights may be left wanting more. Conversely, this pad is likely overkill for dedicated three-season backpackers, who would be better served by the the much lighter Ether Light XT Insulated Air or another top three-season sleeping pad.

But for most winter backpackers, backcountry skiers, alpine climbers, or anyone who simply has a year-round preference for plush backcountry comfort, the Ether Light XT Extreme is an almost unbeatable option from one of the best brands in the sleeping pad space.

 

With it’s air sprung cells and 4 inches of thickness, the Sea To Summit Ether Light XT Extreme is one of the most comfortable winter sleeping pads we think you’ll find.

 

DISCLOSURE

Sea To Summit provided me with a free sample for this review – but the views expressed here are all my own. The review also contains affiliate links, which help us keep churning out more content!

MORE INFORMATION

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Happy hiking and take care out there in the wild!