The first rollerball system was invented by the company Ohto from Japan in 1963. In this technique, the ink feed and the ink are in a barrel similar to a ballpoint pen. In 1995, the Karl Meisenbach KG invented an ink-liner with which one you can also use standard ink cartridges for fountain pens.
An ink roller or rollerball works with a water-based ink, with a ball in the tip to dispense the ink evenly. The difference to the ballpoint pen is the ink. The ball pen is very viscous, rather a paste, but in the roller the ink is more like water, so that it slides even more soft over the paper.
Products: Ink roller, rollerball, with cartridges or refills
Brands: Kaweco, Otto Hutt, Stipula, Visconti, Faber-Castell