Roller ball pens are
pens which use ball point writing mechanisms with water-based liquid or gelled
ink, as opposed to the oil-based
viscous inks found in
ballpoint pens. These less viscous inks, which tend to saturate more deeply and more widely into
paper than other types of ink, give roller ball pens their distinctive writing qualities. The writing point is a tiny ball, usually 0.5 or 0.7 mm in diameter, that transfers the ink from the reservoir onto the paper as the pen moves.