Discover Schmidt's Ink Ball technology When American Pen Company introduced the Independence in a fountain pen and rolling point, they also engineered it to accept Schmidt's ingenious Ink Ball technology. Imagine being able to use pure liquid ink. Even better, you can choose among the 31 vibrant colors we offer. Or, use the converter and dip into your own personal favorite inks. The American Pen Company Ink Ball takes any common international size cartridge.