Gel pen 0.5 0.7 1.0 means that the font thickness written by gel pen is 0.5 mm, 0.7 mm and 1.0 mm respectively. The difference lies in the thickness of writing. Their uses are also slightly different, and they are suitable for different occasions. 1.0 gel pens are generally used for signature marking and calligraphy. Because the written words are thick, marking is conspicuous and easy to mark, but they are generally not used for writing articles. Too thick fonts will make the article as a whole unsightly; In addition, because it is easy to change the thickness of writing, it is more suitable to practice writing. A gel pen of 0.5 is generally more suitable for writing articles. Large-scale exams generally use a 0.5 gel pen. A gel pen of 0.7 is somewhere in between.