Ink cartridges and converters each have advantages and drawbacks. The installation process is also different. For cartridges, it’s quick and simple. Unscrew the pen’s barrel from the grip. If you look at the feed inside, you’ll notice a sharp protrusion of some sort facing out. This is what punctures the cartridge when you install it, allowing the ink to flow down the feed and out of the nib. Insert the cartridge inside the grip and press firmly to puncture. Reassemble the pen and leave it sitting nib down for an hour or two so the ink can travel down to the tip. To refill a converter, install it into the grip section as you would with a cartridge. With a piston converter, there is a knob on the end that twists to extend the piston. Extend the piston and dip the tip of the pen into the bottled ink of your choice. Then simply twist the knob in the other direction, drawing ink into the reservoir. For a squeeze converter, install it in the grip section and dip the nib into the ink. Squeeze the reservoir, releasing the air inside and causing some bubbles to appear in the ink. Release the reservoir slowly, and just like with a piston converter, this draws ink inside. Clean any excess ink off the tip as needed. Some fountain pens are refilled manually with an eyedropper. Others have a built-in filling system, the directions for which vary depending on the manufacturer.