Yeah, they are neoprene, but according to "puting the heads together" in another thread, there's far different types of neoprene. Some are just sponge like mousepads are, which I wouldn't recommend, and some are waterproof/airtight, which is what's needed.
The intent is to stop air from infiltrating the socket area, and carrying moisture with it. In my own oppinion, mousepads aren't good enough to stop this. Also, if it's not airtight, it's not the best insulator either.
If you can blow air through, however slowly, it's the wrong neoprene.
yes mouse pads are neoprine foam where as what we use is neoprine rubber its more dense thus air cant move through it and beacouse of this its also got 10x the heat transfer resistance. mouse pad works Ok if your doing something like a pelt but if your gong to be doing super sub zero be prepaired to shell out a bit of cash.