Unsure what you are asking. There is that rubber boot with the metal ring around it, then the plastic bezel and boot... You can just get some strips of Dynamat if you need anything else. If you mean extra foam around the OEM metal gasket then try ordering the whole unit from a Ford dealer because the aftermarket ones are all just the metal and rubber.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.