For the curious, I took some close-up pics of the "Brand X" diffuser discs that I'm using.
and with a ruler
I am NOT going to count all of the holes - but
4 rows per CM
6 holes per centimeter (looks like hole and space is roughly equal so holes are about 0.5 CM each or 500 microns.)
So . . . 24 holes per CM^2 and a 9" disc is about 346 cm^2 - yields 8300 holes. Subtract 10% (my W.A.G.) for dead space between the sectors yields 7500 holes in a 9" disc.
I didn't ask any of this before I bought - just went with "fine bubbles" but had a question in a PM, so I thought I would share.
