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A compact, efficient ultralight mat that delivers strong warmth with a supportive feel in a minimal package.
Rab says:
When both warmth and low weight are crucial, the Ultrasphere 5 is the ultimate packable, featherlight air mat, honed for fast-paced exploring in demanding mountain conditions. Its groundbreaking design includes two layers of TILT, which boosts the mat’s warmth-to-weight ratio by reflecting heat back towards your body, all for a fraction of a gram. It also features new offset air chambers that trap heat within the construction, allowing you to recharge comfortably without the need for high-volume insulation. Highly comfortable and supportive, the Ultrasphere 5 is the ideal foundation for thru-hiking, bikepacking, and multi-day mountain runs.
Our Verdict
The Rab Ultrasphere 5 LW Sleeping Mat balances low weight with solid thermal performance, weighing 475g and offering an R-value of around 5. It sits comfortably in the high-efficiency 3-season range, pushing into 4-season use.
The tapered shape keeps pack size down while offering a more generous fit than standard versions. At 8cm thick, it feels stable, with a structure that holds you in place through the night, making it a good fit for side sleepers. The added length and width make it better suited to taller hikers or those who prefer space to loung.
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 without time and care (i.e. not quickly packing up in a tent). In practice, it makes more sense to leave it behind and use a simple stuff sack or elasticated band, which achieves the same result with far less hassle.
- Reviewed by Ultralight Outdoor Gear
Features
- The new weight-saving construction uses offset air chambers to trap heat and keep you warm.
- Two layers of heat-reflective TILT reduce radiant heat loss without adding weight.
- Comfortable tapered mummy shape that eliminates unnecessary bulk.
- Soft, exceptionally lightweight 20D fabric.
- When it’s time to pitch for the night, the two-way valve and inflation sack make camp setup quick and easy.
- Thickness: 8cm.
- Packed size: 18x9cm.
- Roll-away stuff sack with repair kit included.
Specifications
- Weight: 475g
- R-Value: 4.9
- Thickness: 8cm
- Packed size: 18x9cm
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
- 100% Polyester Inflatable Mattress with down insulation
