Pilot Frixion Ball Knock Retractable Gel Ink Pen, 0.5mm, 10 Colors (LFBK-230EF-10C) Special gel ink allows to erase your writing by frixion with pen tail Erase and rewrite any number of times without damage on papers 10-color set of black, red, blue, blue black, green, light green, orange, pink, light blue, and violet Ballpoint Size : 0.5mm Not recommended for use on legal or official documents