The Rotring Rapidograph will not clog due to the pre-filled, disposable capillary cartridge. Instead of a normal ink reservoir, the Rotring Rapidograph has a capillary system that combines the ink reservoir and the breathing system in one piece. This means that the pen receives a completely new, clean, pressure equalization system each time the cartridge is replaced. Virtually no maintenance is needed. A double-rotating helix in the cartridge prevents leaking due to ink temperature rise. The stainless steel points are suitable for lettering on tracing paper and vellum as well as for microfilm work. Each is fully equipped with a capillary cartridge, drawing point, holder, double-seal cap and pocket clip.