Therm-a-Rest ProLite Sleeping Pad 50d mini Hex Rip Polyester The lightest self-inflating mattress Therm-a-Rest makes. Die-cut foam and tapered shape provides warmth and comfort with limited bulk. Light, compressible materials make the ProLite mattress pack friendly. Expanding foam core self-inflates; top off with just a few breaths for personalized firmness. R-Value of 2.2