First Look: Sea To Summit’s Ether Light XT Extreme Sleeping Pad


The Sea To Summit Ether Light XT Extreme is a robust and incredibly warm (R-value of 6.2) sleeping pad designed for winter camping, climbing expeditions, and cold sleepers. The pad is constructed with a layer of Thermolite insulation and has four inches of loft. 


Very warm and insulates/pads well against rocky sleeping areas (e.g., alpine bivouacs) // Baffles are supportive and comfortable right up to the pad’s edge // 30/40D Nylon face fabric inspires confidence on rough terrain // Stuff sack is integrated as part of the inflation bag to reduce weight and keep moisture to a minimum while blowing it up // Available in six sizes


On the heavier end of comparable winter pads (27.4 ounces) // Bulky (6.9 x 9.4 inches when packed) // Crinkly, noisy material

Our Thoughts

The Sea To Summit Ether Light XT Extreme is a worthy sleeping pad for climbing missions that prioritize warmth and a good night’s sleep over weight and packability. The pad isn’t a behemoth, to be sure; it packs down to a third of the size of a closed-cell foam pad, and much lighter than a car-camping one. However, compared to ultralight options (with admittedly lower R-values), there is a weight penalty for making this pad part of your luxurious snow-cave bivy. Regardless, the Ether Light XT Extreme’s warmth and four inches of comfort should not be hastily dismissed: for done-in-a-day climbs that require a bivy below the route, multiple days at the same camp, or even cold sleepers who crave crisp sending temps, this pad will deliver.

Size Reviewed

Men's regular


27.4 ounces including pump sack




Sea To Summit

Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.

My first “real” sleeping pad was a thin, yellow foamie that folded up like an accordion and only barely reminded me that I was not in fact sleeping on the cold, rocky ground itself. But I didn’t care. I had just graduated from a military-grade 1980s Thermarest, and, instead of looking like a Boy Scout, I fancied myself a fast-and-light alpinist, taking my minimalistic pad up harrowing AI 2 alpine routes before, inevitably, bailing due to inexperience and fear. 

What I didn’t realize then—and am kicking myself about now—was the importance of a good night’s rest. I skied into many a winter climb with that yellow accordion strapped to my pack, psyched as could be for another -15° F night under the stars. A romantic image in hindsight, sure, but shivering for hours while your precious body heat leeches into the soil is not an experience I’d recommend. While packing up my kit, I’d often lift the foam pad off the snowy ground and see thawed, green grass beneath it. At least something warmed up last night

That’s a long introduction for what is actually a first look at a simple product: a warm and comfortable sleeping pad. I tested the Ether Light XT Extreme for several nights this autumn, down to -10° F, sleeping on snow, talus, and the bed of my pickup truck while chasing prime-sport climbing conditions in the Rockies of western Canada. 


I am 5’10” and 160 pounds, and found the “Regular” size to be a perfect fit. Don’t expect to stretch out at these dimensions; I had to fold my arms over my chest—or keep them stiff at my hips like a corpse—or else they’d fall off the sides. The pad comes in six sizes (strangely, four for men and only two for women) to dial in the fit. 


The Ether Light XT Extreme is designed using “Air Sprung Cells” (think, the dimpled surface of a traditional spring mattress, not the horizontal/vertical baffles of popular pads) to provide support in any sleeping position and cushion the rocks and roots of an imperfect camping site. The pad has an internal layer of Thermolite insulation that makes it feel like there’s somehow a thin puffy jacket inside. This addition is obvious when deflated and contributes greatly to the pad’s overall bulk, but it’s also the source of the pad’s impressive R-value. The pad is treated with an antimicrobial agent to eliminate mold and other disgusting growths. 

On the outside, a 30/40D nylon face fabric improves durability without drastically increasing weight, and it feels solid in hand. I neglected to bounce on the pad at alpine bivvies (now that I’ve learned the value of sleep), but I wasn’t concerned about using it without a ground sheet and I didn’t see any signs of premature wear.

Sea To Summit rolled the stuff sack and pump sack into a single item; it’s not a groundbreaking design by any means, but it reduces weight and redundancy to some degree, and (more importantly) is one less thing to lose in the field. 

In sum, you likely won’t be breaking any speed records with the Ether Light XT Extreme, but for climbs where a good night’s sleep will allow you to rage up the route in a day, or if you’re after a more leisurely jaunt in the hills, this pad will serve you well.

This article is free. Sign up with a Climbing membership, now just $2 a month for a limited time, and you get unlimited access to thousands of stories and articles by world-class authors on plus a print subscription to Climbing and our annual coffee-table edition of Ascent. Please join the Climbing team today.

Trending on Climbing

Film: How Matt Cornell Free Soloed One of America’s Classic Hard Mixed Routes

"The Nutcracker" explores the mental challenges of solo climbing and the tactics Cornell used to help him send the route.