If you want to use bottled ink, or reduce further your use of plastic cartridges, you can fit your fountain pen with this convertor for bottled ink. Unscrew the barrel, removed the cartridge, and replace with this convertor. Twist the convertor to fill with bottled ink, multiple times for more ink, and refit the barrel. If you are changing ink colour, you'll need to flush out the cartridge several times. Its a slow process, so enjoy it. Consider it a form of mindfulness.....