RAB says about the Ultrasphere 4.5
Combining TILT, ultralight fabric and heat-trapping offset air chamber construction, this featherlight air mat offers superb warmth for weight and packability. Highly comfortable, it's the ideal foundation for thru-hiking and multi-day mountain runs. 2 layers of TILT reflective film help reduce radiant heat loss without adding weight or bulk. Offset weight saving internal cut outs help disrupt the flow of convection currents and keep warm air static. R-Value: 4.3. Thickness: 8cm. Packed size: 18x9cm. 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 .