The cloth I have is a rubber backed cloth. I would have to measure it, but I could always send a small piece to let you actually look at it.

Is this going in a fuel pump? Or just what will you be putting this in?

I had an old propane tractor that the diaphragm in the regulator ruptured. Could not find a proper replacement. And the new regulators were a bit steep in price. So I used some of the rubber backed cloth I had to make a new diaphragm. This was about 4 years ago and the tractor still works fine.