"Blue Refill: The refill Ink cartridges for O'Pen Glow, O'Pen 2, O'Pen Pro, and O'Pen Mini.3 pieces per pack.","Black Refill: The refill Ink cartridges for O'Pen 2, O'Pen Pro, and O'Pen Mini.3 pieces per pack. ","Black Refill: Please take note that there is a risk of the plastic cap at the end of the pen refill falling off during the installation of O'Pen Glow."
