Rab Ionosphere 5 Review: A Black Ship Has Arrived in the Mattress World. Rab's First Air Mattress Is the Best Buy of the Season

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Sleeping pads (mattresses) for hiking and mountain climbing tend to be overlooked compared to sleeping bags. However, my experience of over 20 years of following the evolution of mattresses, from the flimsy silver mattresses to the modern day, has taught me that the quality of the mattress has a significant impact on the comfort of your sleep, just as much as the sleeping bag. This is especially true when it comes to mountain climbing in Japan, where there are not many comfortable tent sites with perfect conditions

This season, a breath of fresh air has blown into the sleeping pad world. Rab , has finally entered the sleeping pad market this season. This brand started out by developing high-quality down sleeping bags that are renowned worldwide, and has now grown into a one-stop shop offering sleeping bag and mattress sets.

Originally Rab led the European high-end mountain gear market with a refreshingly uncompromising approach to quality, creating a lineup of high-quality products that earned the trust of many enthusiasts. As a passionate fan of the brand, I am confident that this new challenge will not be approached half-heartedly.

For this first entry, they have prepared several lineups to suit different purposes and seasons, and we were fortunate to be able to provide one of them, the Ionosphere 5 , to our website. I have already had the opportunity to try out the tent for a few nights this spring, so I will now write a review about its capabilities and what makes it so great (and what remains to be seen).

Main features of Rab Ionosphere 5

The Rab Ionosphere 5 is an all-season inflatable sleeping pad for serious mountain activities where high insulation and light weight are a priority. Its heat-reflecting, high-insulation TILT technology, combined with synthetic fiber filling, delivers a high R-value (warmth) of 4.8 while remaining lightweight and compact. While its mummy-shaped design minimizes weight, its ample thickness (8cm), raised side baffles, and all-over anti-slip print ensure a cozy, enveloping sleeping experience without feeling uneven ground. The slim 2-way valve allows for quick and easy inflation using the included pump sack. It delivers top-class performance and ease of use, all at an attractively budget-friendly price.

Favorite points

• High insulation that lasts even during the snowy season
• Thick enough and with a high outer baffle to prevent falling off the mat
• Quiet
• Grip print on the outer surface prevents sleeping bags and pillows from slipping
• Convenient 2-way valve system and dedicated pump sack
• Surprisingly low price for its overall performance

Points of concern

• Slightly heavier than other flagship products
• The grooves between the vertical baffles are rather deep (ideally a flatter surface)
• It's a little hard to get air in

Main specifications and evaluation

Detailed Review

Insulation: Unique insulation construction with excellent warmth-to-weight ratio

First, let's talk about insulation (warmth), which is the most important factor for a mattress. The insulation performance of this mattress (how resistant the mattress is to heat loss) has an objective global standard, ASTM R-Value, of 4.8

Roughly speaking, this is a high specification that allows it to be used year-round in the mountains of Honshu, even during the snowy season. Generally, achieving such high insulation performance requires filling the interior with a lot of padding, which increases the weight, but the Ionosphere 5 has succeeded in keeping the weight to just 550g. The secret to this excellent warmth-to-weight ratio lies in the proprietary insulation system installed inside.

Quote: gearjunkie.com

As shown in the photo above, the inside of the mattress with a heat-reflective film that uses the company's TILT (Thermo Ionic Lining Technology) Stratus™ R insulation ," which are integrated together. The heat-reflective film reflects the heat generated by your body inside the pad, minimizing radiant heat loss, while the Stratus™ R insulation prevents the cold air from the ground from circulating inside, preventing a drop in temperature. The basic mechanism behind the Ionosphere 5

Quote: gearjunkie.com

I actually spent a night on this mattress (I wasn't too worried because the R-value, which has become popular recently, is a fairly reliable indicator), and it certainly lives up to its name. I haven't slept on it in the mountains in the depths of winter yet, but when hiking in low mountains in the spring, I didn't feel the cold of the ground even when I was standing directly on it. In the summer, it's just right for high mountains like the Alps, and in other low mountains, it provides such high insulation that you'll sweat even when sleeping directly on it

Comfort: Thick enough for side sleepers, and thoughtful attention to detail for a stable and comfortable sleep

Since this mat is positioned as one for serious mountain climbing, it is naturally mummy-shaped to make it lightweight, with curves around the face and shoulders and a slightly narrower width towards the feet (see photo below)

The small air chambers (baffles) have a vertical structure. Generally, vertical baffles tend to be said to offer less support (the impact of dents caused by weight is greater) and less comfort than horizontal or box-shaped baffles (although this often depends on personal preference). However, despite this model having a vertical baffle, it has many features that compensate for this weakness and ensure a comfortable sleep

For example, the base is 8cm thick, which is thicker than other air mattresses of the same level. Because of this, even when lying down and resting your elbows on the mattress, or sleeping on your side, your body never touches the ground, and the ample cushioning provides a soft and fluffy sleeping experience

The lightweight 20 denier polyester fabric is reinforced with a TPU coating on the back, so you can rest assured about its waterproofness and durability

In addition, the baffles on both sides are raised by about 9cm to prevent any lateral shifting (see photo below). This, along with the thickness of the base, ensures a high level of enveloping comfort

Furthermore, the regular pattern applied to the entire surface is a grip print that has an anti-slip effect, preventing sleeping bags and pillows from slipping as much as possible (see photo below). It would be great if you could always be the first to arrive at the tent site and secure a comfortable sleeping spot, but things don't always work out that way. In some places, it's not uncommon for tent sites to be slanted, and the tent fabric is also slippery, so in those cases positioning can be very difficult without anti-slip material. So these features are surprisingly important. They can make it difficult to fall asleep and have a major impact on your sleep time

What's even more impressive is that this model does not produce the rustling noise caused by the films rubbing against each other when you move, which is common with mattresses that use metal films, and it is also extremely quiet

Storage and usability: Carefully crafted with ease of use and durability in mind

Although it's becoming almost standard these days, this model comes with a storage bag as well as a dedicated pump sack, which makes inflating the mat much easier and faster than inflating it by mouth

The Ionosphere 's air inlet uses a 2-way valve system with a double cap for "inflation" and "exhaust" (see photo below). It has relatively little protrusion and is flat against the mattress surface, so it doesn't get in the way when you sleep or store it away. It's also durable, so you can rest assured.

To set it up, open the top cap of this valve and insert the opening of the pump sack. The pump sack has a large capacity, so I was able to fill it up to the maximum in just a little over two tries. Generally, it went very smoothly, but perhaps because the opening is small, it was a little difficult for the air to enter

By the way, be sure to check out the playful pump sack design (photo below)

When the main body and pump sack are stored together, they become quite small, about the size of a Nalgene bottle (see photo below)

Cost performance: High overall performance, including price

As we've written so far, the Ionosphere 5 offers impressive performance in every way, but it's by no means the lightest, most compact, warmest, or most comfortable mattress on the market.

So what is the true appeal of this mattress? In my opinion, it is its high overall performance, including its price. To make it easier to understand, I have created a performance comparison table between competing products, which is something I don't usually do

The table below compares three typical sleeping pad models with similar R-values ​​(mummy-style air mattresses with R-values ​​of around 4.5 to 5.0) that you would likely consider when purchasing this model. The model with a gold background is the model with the highest performance, and the light blue background is the model with the second highest performance

Looking at this, the Ionosphere 5 is slightly heavier, but it has a higher R-value than the Thermarest, and is roughly equal in mat size, storage, and durability, and is superior in some areas of comfort, such as quietness and slip resistance. The Nemo Tensor Alpine series is also quite hard to beat, but when it comes to deciding which one to buy right now, the price difference is hard to ignore (of course, it's still not cheap for everyone).

Comparison of major models of all-season mummy-type air mattresses

Summary: Recommended for these people

Rab Ionosphere 5 Unisex Regular Zest

created by Rinker

RAB

¥24,200 (as of 2026/02/19 08:24:29, according to Amazon - details)

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As I wrote in the main text, this mattress may not be a model with outstanding performance or cutting-edge functionality

However, it has high insulation properties that can withstand snowy weather, weighs only around 500g even with the stuff sack inside, and is undoubtedly of high overall quality (no weaknesses), including a thickness of 8.0cm, comfort, and ease of use

In addition to this excellent balance at a high level, and especially considering the price, which is clearly more affordable than other models, we can't help but conclude that there is no model this season that is more worth buying than the Rab Ionosphere 5

I think there are many people like me who can't keep up with the recent price hikes on high-end mountaineering mattresses. For those looking for a lightweight, comfortable, and versatile mattress that can last all winter, this is the perfect choice. Even if you're just starting out, you'll be very satisfied. Whether you're a long-time Rab fan or new to Rab, we hope you'll experience the new, reliable quality

   

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