Well, ummm... I own several baoer fountain pens, each one ships with identical screw converters...that work pretty decently. BUT: if I detach them and try to shove a international/standard/peilikan type cartridge, it simply doesn't fit. If I do it by brute force, it results in most of times, a cracked cartridge and ink everywhere....or in the worst case a disassembled/pushed forward nib/feeder. It's not just a single model/single package baoer pen, but 4models from different sellers and shapes. Plz explain me: am I forced to use that default bad-looking, cheap converter?