Hello!!
Have you the same number of models of the same brand: Do you realize if everyone has the same form of tip plumín or there may be variations between each other?
I have seen some plumines, and especially tips of different brands and each has its peculiarities and I think that should be a science and have such expertise to put in the tip of these "droplet" of iridium, which we all know is the hardest mineral that exists and more malleable little over land and foremost that this "droplet" is perfect and divided into two equal and symmetrical where the ink to flow to the touch or finesse writing that characterizes each brand and model.