Most contemporary fountain pens are cartridge-converter pens, meaning they can use either disposable ink cartridges or a removable ink reservoir known as a converter to supply ink. Many ink cartridges are proprietary to their own brands and are not interchangeable with pens from other manufacturers - consult our Inks page for more information. Cartridges are intended for one-time use only and are discarded when empty.
Converters, on the other hand, are reusable and allow for filing with bottled ink from any fountain pen ink manufacturer. They are also very useful for cleaning your fountain pen even if you only use cartridges for your ink supply - take a look at our pen maintenance page for more details.
A piston-filler, such as almost all Pelikan and some Omas, Pilot, and Sailor brand pens, has a built-in reservoir and filling system that allows the pen to be refilled by dipping the nib directly into an ink bottle while twisting a knob or piston at the end of the pen barrel. Piston-fillers often have a larger ink capacity than cartridge-converter pens, leading to their great popularity among many fountain pen enthusiasts.
Much rarer is an eyedropper filler, such as the Bexley Imperial, in which the entire sealed barrel can serve as an ink reservoir and which can be filled, as the name suggests, by an eyedropper or syringe. Other older styles also exist - vacuum and bladder fillers, lever fillers and crescent fillers - but these are largely relegated to vintage pens or recreations of them.
Feel free to call or write us if you are not sure which filling system you should want or need, or if you are not sure what kind of system is used by the pen or pens you are interested in.