Toho pen

Dispenses a water-based ink through a ball tip similar to that of a ballpoint pen. As such, gel pens might be considered a subcategory of rollerball pens; however, due to the widespread knowledge and use of the term 'gel pen', 'rollerball' is in practice typically reserved for pens which use liquid ink.

The lower viscosity of rollerball ink compared to oil-based ballpoint pen ink has several effects on the pen's performance.