Calligraphy pen?

From Lamy there is a triple set of calligraphy springs mounted in cartridge fillers. I think these are 1,2,3mm line width. There are three ink cartridges that have the usual double ink volume “normal” cartridges.

From other manufacturers there are Spring holder and springs for immersion. It’s cheaper, but it’s a bit more difficult to write. On and below these springs it is possible to push ink holders, which hold more ink by capillary forces than the spring not equipped therewith. In order to test your own grinding of springs, these parts are probably better because the springs are not so expensive.