does anyone know dimensions of exhaust seal?

[Livolsi, Stephane]

I am looking to replace the doughnut shaped sealing washer between the first
exhaust section and the middle section (right around the transmission area)

Family Album says the part # is 853-253-137 (thanks again, George)

No local Audi dealer and I was hoping to get a generic replacement at a
flaps.  Does anyone know what size I should ask for?

Stephane