I'm looking into replacing the top arms or even all the arms on my front suspension but a bit confused.

Are all A4 arms the same across the B5, B6 and B7 platforms, specifically the length etc?

So far I've found the majority of kits are for 16mm or 20mm ball joints but I can't seem to find out if its upper or lower ball joints that are sized. I know my car, 1.9 B7 has 16mm upper ball joints but the lowers look larger.

Hope someone can shed some light on this as there's not a lot of info on the internet about them!!

Thanks Alan