This is the hocoro Dip Pen Double (2 Nib + 1 Barrel), a part that makes it easier and more convenient to use bottled ink for fountain pens with the hocoro Dip Pen.
The "hocoro Dip Pen Double (2 Nibs + 1 Barrel)" is a product that includes one pen barrel and two interchangeable nibs.

Play with more ink colors, the casual and durable way.
You can enjoy a wide variety of fountain pen ink colors without the conventional messy fuss.
All you need to do is simply rinse the nib with water and wipe dry.