Therm-a-Rest UltraLite

This is exactly what is claims to be. It is an ultralight self-inflating pad that is perfect when it's not too cold and light weight is the biggest concern.

I've used mine for two full backpacking seasons. It is only about 3/4 inch thick but very comfortable. It weighs less than a pound (mine is the 3/4 length version). I fold it in half and then roll it up to just larger than a nalgene bottle. I overinflate it but it has been very durable and supports my 220 pounds without any damage.

For extra heat insulation and comfort I sometimes combine it with a full length Z-rest. Together still under 2 pounds. The UltraLite was replaced by the similar ProLite 3 just after I purchased it.

I think the ProLite 3 has better thermal insulation and a full length ProLite 3 MIGHT eliminate the need to add a Z-rest (not sure).