Yookers pens come in various series, the Metis, the Eros, the Yooth. Replacement tips vary for the different series of pens. They all are felt-tip and literally glide across a quality paper. And, they're refillable with a simple international ink cartridge. Even more enticing are the choices of four writing tips from extra fine to a nice broad line. Options for the closed-out Gaia pens are limited. Choose your favorite design and then add a few tip choices!