The sub diameter at the top is 45cm on my FL S3 Sportback with B&O and has a spacesaver wheel. As others have said, it should have Bang & Olufsen embossed on the top per other pics in the thread.
According to the thread below, subs for the Audi Sound System (at least the early ones) were made by PSS, and the 2012 subs don’t fit into 2015 cars:
I been reading posts for ages and have finally registered! I recently took delivery of my sportback 1.6tdi Daytona Grey S line. My one regret is not taking the advice of my dealer to add the Audi Sound System, but I assumed the standard system in the 8V would be as good as my 8P which had a sub...
www.audi-sport.net
@toaophil:
do you have an A3 or S3?
If an A3 is it Quattro or FWD?
what year is your car?
Did it come with B&O and this sub or are you retrofitting / acquired the sub separately?