This is the name of a line of sleeping pads made by Cascade Designs in Seattle. They are constructed of foam inside an airtight covering. When you open the valve, the foam slowly expands, pulling air into the pad. You top it off with your breath, then you close the valve and you've got a nice surface to sleep on when you go camping or rafting. When you open the valve, you can squish the air out and roll the pad into a very small, compact bundle.