Hongdian Fountain Pen Ink Cartridges Black Color Set, Pack of 30 Ink Refill Cartridges, 3.4 mm Bore Diameter

These cartrides compatible with fountain pen takes 3.4mm cartridges such as Hongdian matte black forest pountain pen How to fill a fountain pen with cartridges: Insert the narrow end of the new cartridge into the black of section block with enough pressure to create a snug fit. The pin inside the section block will puncture the seal of the cartridges, allowing ink to flow into the section block...