The Rab Ultrasphere 4.5 was super popular from the day of its introduction, and for good reason. Now Rab has taken one step further, and thanks to increased insulation the model has received a new name: behold the magnificent Ultrasphere 5! Rab brings together a whole bunch of technologies and materials in the Ultrasphere pad family. They boast a double appliance of TILT technology, which reflects some of your body heat right back, with minimal weight penalties. This model boasts insulation perfect for three season use, and also good for mild winter conditions, especially if used on top of a closed cell foam pad. Compared to the previous 4.5 model, this 5 is warmer (R value 4.9 vs. 4.3), but it is even lighter than the 4.5. The Ultrasphere lineup is designed for thru-hiking, bike-packing and multi-day mountain running - uses where every gram counts. Due to this, we recommend you be careful about where you set your pad, as the fabric is in the ultralight category of materials. It's w