John, the Everglass is fiberglass reinforced. It is a short strand fiberglass. Evercoat
There is a longer strand fiberglass like Kitty hair.
Then of course the long strand Tiger Hair
I have found that these products are an amazing quality. Being the rust is merely a hole and not collapsed in or anything like that the shortest hair would be my choice because it is o easy to work with, not much different than regular "bondo". The Tiger Hair is crazy difficult and only needed for busted up fiberglass or something like that. It is a serious PIA to work with.
That Everglass is a killer product for something like this.