Rollerball Refill
Rollerball refills are water-based and produce a smooth, inky line. Refills are different for capped or retractable rollerballs and also some brands like CROSS and LAMY take their own proprietary size. Look out for a ceramic ball over a steel ball, which is harder wearing and more likely to remain smooth for the life of the refill. Gel refills are another variation, which although not quite as smooth as a liquid rollerballs, dry faster.
