What's it for?
This converter from Schmidt is a standard international size, which means it can be used with a wide range of fountain pens. A converter is essentially an empty ink cartridge, which you can fill with an ink colour of your choice.
How does it work
Simply unscrew the nib section from your fountain pen, and remove the empty cartridge (if applicable). Insert the Schmidt K1 Converter, and twist the end to ensure the plunger is down. Then dip the end of your nib into the ink, and twist the end of the converter once more, which will suck up the ink (similar to how a syringe works). Once filled, you can wipe off the nib, and screw the nib back into your fountain pen to begin writing.