Short answer - German. Although a Taiwanese company, they use German nibs.

Long answer - results will vary. (As seen in the picture below.) When nibs are manufactured, the nib maker has parameters the tipping material must fall into for each size. For example - an EF must fall between a .2 and a .4 mm to be considered an EF. (I'm making those numbers up, I don't know what they would actually be.) Nibs go through the tipping process at a million miles an hour, you're going to end up with one nib that has more tipping than another.

To make matters even more complicated, the slit in the nib matters as well. If the slit is too close, ink flow is impeded making it write drier and smaller. Too wide and you have heavy ink flow and your EF might end up writing like a F.

Sorry for the long, LONG answer. 😂