Rollerball can be refilled with the exchangeable One Change cartridge with Ultra-Smooth tip for the best writing experience. Line width approximately 0.6 mm, waterproof according to ink standard ISO 14145-2. The innovative Super-Flow-System guarantees consistent ink flow from start to finish. The cap-off ink does not run dry even if the cap is removed for 2-3 days and, besides this, is quick-drying and smudge proof. The One Change has a sturdy metal clip and a rubberized grip zone that provides a secure hold for relaxed writing. Sold as 1 pen.