Shift Lever Diameters?

Hi all, I'm a newbie conducting some research and could do with your help!

Aftermarket shift knobs labelled "universal fit" usually come with gearshift stick adaptor tubes with 8, 10, 12, 14mm internal diameters to
allow them to fit on to gear shift levers.

The issue is, many cars have widely differing gear shift lever diameters from the above measurements, and as a result, my organization gets a lot of feedback from buyers complaining of shift knobs that can't be installed on to their gear shift levers.

I would appreciate it if anyone could provide me with a clue to where, or how, I should go about collecting the data i require. I have gone through the usual search engines hunting for vehicle schematics, to no avail. Thank you all for taking the time to read this.

And what is NO MA'AM going to do with these numbers? and just what is the organisation about anyway?

if this is genuine advertising im going to crack the shits.

I would go to various wrecking yards and take the measurements myself.

Yeah, that's what I reckon I'll do. Besides, I sorta figured that auto manufacturers probably only vary shift lever diamaters by a wee bit here and there, or none of the aftermarket knobs would ever fit properly.

As for NO MA'AM, this is what we're about (http://www.bundyology.com/nomaam.html)...I would say you're probably members already, without knowing it.