The closed line is not protrude quite right only where you want to check from looking characters from the window of the pen tip. Water resistance, light resistance.
Large windows with pen core is visible character
I adopt a transparent pen core large windows of about 7mm square marked with the pen tip. The closed line is not protrude pita only place from looking characters from the window, you want to check.
One pen, such as in the form of beetle horns, three wire-thin line, thick double line (line box) is closed. As a conventional twin marker, there is no need to brought back the top and bottom of the pen to use different pen.
Order can be marked so as to enclose the character, double line, we maintain the legibility without wearing any character you want to copy.