They are comfortable to write all day and give s great end product with a fine line

They are not so slippery as a roller, more like the feel of writing with a fountain pen, not much pressure gets you a solid line.

Clean lines and even ink flow

Fine, smooth line and the ink doesn't bleed through the paper

Fine, smooth line and the ink doesn't bleed through the paper

That being said, with a few improvements it would be perfect!I am very particular about clean, fine lines, so these were an obvious choice.