The ink level of the cartridge can be seen at a glance, eliminating the frustration of undetectable ink left until you write it. This is a direct liquid type that can be replaced with a cartridge. Replacing is clear and easy to replace. Perfect personal equipment for cram and seminar teachers who always use dry erase markers. From the start to the end of use, we adopted a dark ink that is clear and easy to see. The bold writing is perfect for large conference rooms, schools and cram schools. The included replacement tool allows you to easily replace the nib. It can be used repeatedly and economically. Please be aware that there may be differences in erasability due to whiteboard surfaces. Cartridge Replacement; Oil-based ink (alcohol-based); Ventilation cap; Material/Shaft/Cap/Cartridge/Cover: R-PP; Ink Color/B: Blue, D: Black, G: Green, R: R; Type: Fine Point. External Dimensions (Shaft Diameter / Length): φ21/135