The BIC Gel-Ocity Illusion black rollerball pen writes very smoothly. The black ink in the gel ballpoint pen is erasable, thanks to the thermosensitive technology. By rubbing the end of the pen over the written text, the error is a thing of the past. The BIC Gel-Ocity Illusion rollerball pen has a point width of 0.7mm and a writing width of 0.35mm. The narrow line width allows you to write accurately and in detail.