Pilot CON-40 Piston Twist Fountain Pen Ink Converter

The Pilot CON-40 Piston Twist Fountain Pen Ink Converter is a small refill mechanism that lets Pilot cartridge/converter fountain pens use bottled ink instead of disposable cartridges. It uses a screw-style piston system that draws ink directly into the reservoir when you twist the end, making refilling simple and reusable. 

Inside the clear body, there are tiny metal agitator balls that help break up air bubbles and keep ink flowing more consistently. The converter holds about 0.4 ml of ink, which is on the smaller side, so it may need refilling more often during longer writing sessions. 

It is designed specifically for Pilot’s cartridge/converter system pens and fits models like the Vanishing Point, Prera, Kakuno, and others. While it is convenient and easy to use, it is generally considered a basic, compact option rather than a high-capacity converter, which is why some users prefer alternatives for heavier writing.