You knows what's interesting? I purchased several 9 inch diffusers from Ebay, Amazon, and Vertex. Except for the color they are all identical including pore size. My guess is they are made by the same manufacturer.
Did you ever measure the pore sizes and count numbers?
I think that would be kinda tough on the fine bubble rigs, but you can measure them on the medium and coarse diffusers, at least the ones I have.
