Hi Charlie,
I received this vent from MDA as a free-be which upon further inspection before taking the photos I noticed that the back side is scratched (no protective film) but thankfully the other side has the film and no scratches. Looking at the vent edge-on I have noticed there is a slight buckle in between the centre holes which I think could be made flat without too much fuss.
Size is 18 1/8th inch x 11 7/8 inch.
I really have no use for this vent, let me know.
Chris