You can add your favorite color ink to change the look. Of course, not only TWSBI ink, but also various ink colors can be used. Transparent so you can see the ink level at a glance and never worry about running out of ink. The traditional ECO has a hexagonal cap and butt shaft, whereas ECO-T has a smooth triangle. The grip has also been improved so that the handle stays in place. The high-tech and sophisticated stainless steel nib smoothly runs on paper for inspiration. This is a professional fountain pen with an inhalation type that says ECO, and once you fill it with ink, you can write for an amazingly long time. Can be disassembled and cleaned using the included wrench.