Flex Air Mattress

Recently, I came across a pad that looked so good, I ordered two and tested them the night it came. The bits first: 2026 Rab Ultrasphere 5 Long Wide R5.5 16.65oz (weighed) 3.5” height Packed size 7.5 x 3" (packed size, measured after repacking from factory folding) 77 x 25"  2026 Rab Ultrasphere 5 Medium Wide R5.5 15.50 (weighed) 3.5” height 7.25 x 2.5" (packed size, measured after repacking from factory folding) 72 x 25" [Pad link](https://rab.equipment/us/ultrasphere-5-sleep-mat?utm_source=google&utm_medium=cpc&utm_campaign=21291738690&gad_source=1&gad_campaignid=21291738690&gbraid=0AAAAAC6UPyu5ojG1SA54Br2S9DmL8pdro&gclid=CjwKCAjw8arQBhB9EiwAfIKdQmWEKNs7TltFNvhwXw5-mtZ_NUK6ghIsz0P4Zt7RhLMQN_ADI1WBpxoCPpEQAvD_BwE) Lately, Ive been testing the Nemo Tensor Elite as well, so naturally I took them both out the same night. Loved both. Like - real love. Comfort Comfort on Rab is fantastic, similar to Zenbivy Flex Air. (Comfort on Tensor Elite is just as fantastic too, btw.) They pack down to about the same mind-blown small size.   Size The Rab packs down to 1/2-1/3 of the Nemo Eclipse of the same size. With a tarp and this pad and maybe a Timmermade false bottom bag we might be talking SUL holy trinity. Warmth Tensor Elite without a GG Thinlight underneath is comfy for me down to 45-40F. Ultrasphere 5 is good down to mid 20s, warmth just a tad colder than Zenbivy FlexAir. What I’m surprised no one is talking about it. This and Tensor Elite are easily the best pads of 2026 so far. Cons Few so far. I don’t think it sleeps quite like R5.5, more like R5. Still to be tested. The deflate valve is crappy and hard to deflate, but works regardless. Could be a taller pad too. Time will tell, of course. I asked Justin Outdoors to test it, he’s got one in queue. This is the brand new and revised 2026 Ultrasphere 5 version, not the largely failed Ultrasphere 4.5 which tried, but didn't measure up at all to warmth and had widespread durability issues. Looking forward to your thoughts.

Trust me, mate. Obsessive about this stuff. The gear testing I do is bonkers. I stayed up till 5am for two nights straight, laying on pads for hours and recording notes and temperature readings at every point. Been doing for 20 years and absolutely love doing it. At this point I can tell when the pad is warm at 26 vs 23F. In my experience, a rule of thumb for newer pads in the past few years is that 5F pad comfort is generally hovering around 28-24F. R5.5 is a few degrees lower. It's not an exact science and every person is different. I'm just giving my info for what I've experienced to give a reference point. I generally get colder when I'm sleeping, so this pad may be warmer for some people too.

Big three: Shelter John Abela's (RIP) original 9x7 custom dyneema tarp 3.55oz HMG original full protection bivy 6.7oz (not their bug bivy) Pack Bonfus Fastus 23L 12.3oz Pad Nemo Tensor Elite for 40F+ This Rab pad for 40F and lower Bag 40 Timmermade custom false bottom bag (ordering) 11oz HMG 40 sleeping bag for now 14oz The kit is focused on SUL and low volume, but ultimately, comfort. I also carry a custom ultralight aerogel sit pad, three lanterns for photography, downie, full Alpha base layer kit, Zenbivy down pillow and a couple other niceties. Just at or below 6lbs currently.

Base weight is around 6lbs, not 2.9. I don't treat water since it's clean where I hike. Stakes are the 7G blue ones and the sadly discontinued @stakes. Minimal ditty and minimal first aid. Kojin alcohol stove-based 4.3oz cook kit. I don't count photography gear cause it's professional cam gear that I sometimes take and sometimes leave at home. Food bag is simple thick dyneema - no bears really above treeline here. No pack liner - bag is fully waterproof, no phone and minimal electronics other than home-made lanterns - focus is on the mountains.

That’s an interesting one. Eclipse is much taller and a bit more comfortable than the Ultrasphere. In fact, it might just be the most comfortable pad out there. But. When i shined my flashlight through the Eclipse to see the interior coverage, I was really bummed to see that there’s zero insulation on the two big outside baffles. From what I understand, others don’t have it either. So I’m testing which pad is colder. My gut is that I will still prefer the eclipse for comfort, but will end up taking the ultrasphere because it’s much lighter and much much smaller packing

Fantastic comes with a grain of salt, of course, because these are all ultralight beds. That said, try deflating the Tensor Elite a bit more. I find that with the newly released Zenbivy pillow, additionally stuffed with a Montbell Plasma jacket, the comfort is great for both. So good that it comes close or maybe even above the Zenbivy Flexair pad, which IMO, is one of the most comfortable UL pads out there. Everyone's different though. My two cents.

Thanks for the post, Bourbon. Glad you also saw how comfy the pad was. As far as warmth. Actually, I didn’t have a GG pad underneath when I was using it and it was still really warm near or below freezing. What I think may have happened to you is the inflation went south. The only shitty thing about the Ultrasphere that I see is the valve. It’s really hard to deflate and mine will leak slowly if I forget to close the second valve. To close that second valve completely you need to push it in through two sets of plastic ribs. If you just push it past one it’ll be offset and the deflate valve can likely still leak through it. I bet that’s what happened and the valve deflated slightly, so your hip ended up being near or touching the ground. Being near the ground is going to take a lot of warmth an away, almost as much as being on the ground. Two, you may have not deflated it fully for your weight. I actually deflate mine a good bit after fully deflated for it to be even more comfortable. I’m a side sleeper too. The only other thing I could think of is that you may have slept with your hip on an exposed rock that was protruding right where the cold spot was. If that’s the case, all pads will have an issue with warmth in that area. Hopefully that helps.

I don't get what you're trying to say. We're not talking about Nemo or Thermarest pads in this thread. The Rab pad is a high-quality 20d weave that I feel confident about after sleeping on it. Also, all of my 10d pads have been with me so far for years and I've never had a problem. You just need to be careful and get sharp sticks and rocks out before you lay your pad down. It's a non-issue if you take care of your gear.