Rapidograph pens have an airtight double-seal cap that allows instant startup and a see-through cartridge. Can be used with lettering devices. Metric point size designations are in millimeters and nine of the Rapidograph line widths are designed to simplify the task of matching line widths to reduced or enlarged drawings. All Rapidograph Technical Pens include pen point, cap, holder and empty ink cartridge. Koh-I-Noor Technical Inks sold separately. Rapidograph pens can be used with no. 72D stainless steel replacement points.