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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 MW Sleeping Mat balances low weight with solid thermal performance, weighing 441g and offering an R-value of around 5. It sits comfortably in the high-efficiency 3-season range, which I'd be happy to push into light 4-season use.
The tapered shape keeps pack size down while offering a more generous fit than standard mats. 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 width provides more room to settle in camp without feeling 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 without time and care, especially when packing away quickly 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
- 2 layers of TILT reflective film help reduce radiant heat loss without adding weight or bulk
- 20D recycled polyester outer
- Offset weight-saving internal cut outs to keep warm air static
- Tapered mummy shape to save weight
- 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: 441g
- 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
