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A warm and comfortable insulated mat that balances support and reliability for colder conditions
Rab says:
Engineered with precision to deliver exceptional warmth in a compact size, this insulated air mat is ideal for alpinists and adventurers exploring in winter conditions. With a heat-reflective TILT lining and air-trapping Stratus™ R insulation, it reduces heat loss through both radiation and convection, offering you a comfortable sleep on frozen bivi ledges and clear nights at altitude. Low on weight, high on comfort, it thrives on long-distance ski tours, winter fastpacking trips, and multi-day ascents.
Our Verdict
The Rab Ionosphere 5.5 Sleeping Mat offers a strong combination of warmth and comfort, weighing 661g and featuring an R-value of 5.5. It suits colder 3-season use and pushes confidently into winter conditions.
At 8cm thick, it feels very supportive. The long vertical baffles suit side sleeping, while the mat’s oversized side baffles help cradle you and keep you on the mat at night. Big fan of the rectangular shape, which means a few more grams but a larger sleeping surface that feels less restrictive.
The included pump sack is efficient and straightforward to use, weighing 68g, and makes setup quick while avoiding moisture build-up inside the mat.
The mat looks impressively small in the supplied stuff sack. Though getting it back into the bag can be frustrating, especially when packing away quickly in the confines of a small tent, it makes more sense to use a simple stuff sack or an elasticated band instead.
Overall, this is a dependable option that combines warmth, comfort, and a stable sleeping platform for colder nights on the trail.
- Reviewed by Ultralight Outdoor Gear
Features
- TILT reflective film within the insulation helps reduce radiant heat loss
- 20D recycled polyester upper
- 30D recycled polyester base for added durability
- Lightweight construction uses air and insulation for superb warmth-to-weight ratio and minimal pack size
- Oversized outer chambers help keep you centralised on the mat
- Low-profile two-way valve for easy inflation and deflation
- Pump sack included for rapid and hygienic inflation
- Roll-away stuff sack with repair kit included
Specifications
- Weight: 661g
- R-Value: 5.5
- Thickness: 8cm
- Dimensions: 183x51
- Packed size: Regular 24x12cm
ASTM R-Value:
From 2020, there is a new industry standard for measuring the R-value (level of insulation) of sleeping mats – ASTM F3340-18. This new standard is the sleeping mat equivalent to the EN rating for sleeping bags.
You can now directly compare the R-value of mats rated using the ASTM F3340-18 with confidence that is a fair and accurate comparison between mats. In simple terms, the higher the R-value, the warmer the mat.
In general terms, an R-value below 2.0 is for summer use, 2.0 to 4.0 is for cooler 3 season use and 4.0+ is for winter temperatures. This will be also be dependent on your sleeping bag, how cold you sleep etc. Please contact our customer service team if you need advice on choosing the right mat for your activity.
Material & Construction
- Stratus™ R insulation traps air and reduces heat loss from convective currents
- 100% Polyester Inflatable Mattress
