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 bulkOffset weight saving internal cut outs help disrupt the flow of convection currents and keep warm air staticR-Value: 4.3Thickness: 8cmPacked size: 18x9cmTapered mummy shape to save weightLow profile two-way valve for easy inflation and deflationPump sack included for rapid and hygienic inflationRoll-away stuff sack with repair kit included