Pilot Acroball Ballpoint Pen Black Ink Refills, 0.7mm, BRFV-10F-B, Set of 6 (Japan import) [Komainu-Dou Original Package] Refill for Pilot Acroball Ballpoint Pen Black 0.7mm (BAB-15F-BB) Smooth oil-based ink "Acro Ink" Ink color: Black The diameter of a ball: 0.7 mm. Medium type.