I have a very old Snoqualmie Sombrero from the days before they were water proof.  The outer layer is some kind of a brown cloth with a slightly fuzzy covering, not sure what it is called.  The hat is nice and warm, and the ear flaps are great.  I tried one of the newer rain proof ones a couple years ago that had what looked like a black nylon covering, and while it was a good hat, it was not nearly as warm as my original, so i sent it back.  If something happens to my old one I will get another, even if not quite as warm.  As durable as it has been though, about the only worry is misplacing it.