Roller tip pen which use ball point writing mechanisms with water-based liquid or gelled , as opposed to the oil-based inks found in . These less viscous inks, which tend to saturate more deeply and more widely into than other types of ink, give roller tip 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.Roller tip pen which use ball point writing mechanisms with water-based liquid or gelled , as opposed to the oil-based inks found in . These less viscous inks, which tend to saturate more deeply and more widely into than other types of ink, give roller tip 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.Roller tip pen which use ball point writing mechanisms with water-based liquid or gelled , as opposed to the oil-based inks found in . These less viscous inks, which tend to saturate more deeply and more widely into than other types of ink, give roller tip 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.