The Roller Ball Pen comes equipped with a black Quick Drying Gel Ink Cartridge.
Remove the cap, then unscrew the barrel of the pen. When unscrewing this pen, be careful that you don't lose the spring which is installed at the top of the ink cartridge. Remove the used ink cartridge and replace with the new cartridge. Be careful to keep the small spring in the top of the pen barrel, on top of the ink cartridge.