Closed Cell Foam Mat
This is a lightweight bedroll that fits easy to the base straps on the outside of your pack. Provides extra comfort when camping out but most importantly protects you from the cold. The most important factor in keeping you warm while you sleep, is what you sleep on. We lose up to 70% of our body heat through the ground, so if you are sleeping on cold ground with no insulation, you are going to get cold quickly. Closed cell foam is one of the most inexpensive and effective forms of heat insulation in bedding that's available.
If you want a bit of extra comfort but don't want to get cold, put this mat underneath an inflatable mattress and you'll be comfy and toasty warm.