Line thickness indicates the thickness of the writing produced by a particular writing instrument on paper or other surfaces.

The ball diameter indicates the size of the ball found in a writing instrument, such as a ballpoint pen, which is responsible for transferring the ink. In some brands, this value is specified instead of the line thickness of the pen. There may be a difference between the ball diameter and the line thickness, as they do not necessarily correspond to each other.

The ink of the signature pen is non-removable, water-resistant ink and UV-resistant.