Yes, everybody has problems fitting parker cartridges to pens that are designed to take the international standard short cartridge. parker cartridges don't fit, they aren't designed to fit pens other than parker pens. Can't remember the dims but the parker is a 3.4 mm diameter cartridge and the international standard short cartridge is 3.2mm. Dims wrong, principle right.
Fundamentally the cartridge market is dominated by two types, parker and the international standard short cartridge. I think I am correct in stating that all the pens that we make take shorts.