These gel pen refills are compatible with the Sakura Ballsign ID Series in-store: Sakura Ballsign ID PLUS Gel Pen—Silver Metal—0.4 mm and Sakura Ballsign ID PLUS Gel Pen—0.5 mm.
Ball diameter: 0.4 mm / 0.5 mm
Ink colour: Pure black, night black, forest black, Mocha Black, C.assis Black, Mysterious Black.