Wandering Adventure Party

@NullNowhere right, the physical dimensions are all over the place, but fundamentally the inner bore is wider for Chinese pens, so you’re fitting a 2.6mm diameter post into a 2.4mm diameter hole in an international cartridge

@NullNowhere Chinese pens actually take the Chinese standard 2.6mm which is slightly wider than international 2.4mm. Most of the time it works fine with international, but you do need to use more pressure to get the cartridge in, this is normal.