Ultrasphere 1.5 Sleeping Mat – Regular

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The Rab Ultrasphere 1.5 is an incredibly lightweight and packable sleeping mat for warm-weather adventures. The included stuff sack is convenient on the trail. It offers moderate warmth and is a minimalist option for summer backpacking.

Rab says: 

Combining ultralight fabric and heat-trapping offset air chamber construction, our lightest mat offers maximum packability for when every gram counts. Highly comfortable, it’s the ideal foundation for summer thru-hiking and multi-day mountain runs.

We’ve slashed weight and volume wherever we can with the Ultrasphere 1.5, crafting the definitive sleep mat for when every gram counts. It uses innovative offset air chambers to disrupt the flow of convection currents inside and trap heat, keeping you warm on wild overnights without the need for bulky insulation. Combined with a soft, exceptionally lightweight fabric, its weight-saving construction makes it ideal for summer bikepacking, thru-hiking, and multi-day mountain running.

With a comfortable tapered mummy shape that keeps things compact, the mat is thick and supportive, so that you can catch vital rest and restore the energy reserves needed for your action-fuelled days on the trail. When it’s time to pitch for the night, the low-profile two-way valve and inflation sack make camp setup quick and easy.

Featuring an included repair kit, the Ultrasphere 1.5 is fully equipped for your multi-day trips where low weight and bulk are critical.

Our Verdict

The Rab Ultrasphere 1.5 is an incredibly lightweight and packable sleeping mat designed for weight-conscious warm, weather adventures like thru-hiking or fast-packing. Weighing just 365g, it uses innovative offset air chambers to trap heat without bulky insulation. The 20D recycled polyester fabric is soft yet durable. The tapered mummy shape saves even more weight and packed space. 

I appreciate the provided “roll-away” stuff sack that holds the mat. While I wish it were slightly larger, it’s adequate for a leisurely roll on flat ground. However, when packing in a hurry inside a tent, it’s a bit too small.

While only moderately warm with an R-value of 1.3, it’s a great minimalist option for summer backpacking. Inflation is easy with the included pump sack. The low-profile valve and included stuff sack with repair kit add convenience on the trail. For those counting every gram, the Ultrasphere 1.5 delivers a comfortable and surprisingly warm sleeping pad at a fantastic weight. It makes a great ultra-lightweight sleep system component for fast-and-light adventures when shaving ounces is critical.

– Reviewed by Ultralight Outdoor Gear

Features

• Offset weight saving internal cut outs help disrupt the flow of convection currents and 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: 365g (excluding bag)
• Pump Sack Weighs: 44g
• Dimensions: 183 x 51cm
• Thickness: 8cm
• Packed size: 15 x 9cm
• R-Value: 1.3

Material & Construction

• 20D Recycled Polyester outer fabric with internal TPU Coating and fluorocarbon free DWR
• Main: 20D 100% Recycled Polyester TPU coated

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.

Help & advice:

• The Ultimate Guide to Choosing an Ultralight Sleeping Mat
• Time-Saver Guide to Choosing a Sleeping Mat
• About Rab
• Rab Sleeping Mat Guide
• Rab Sleeping Mat Technology Explained
• Rab Sustainability and Responsibility
• R-Value Explained
• Recycled Content in Outdoor Gear