This item is a ballpoint pen unit for a customisable multi-function pen. Outer barrel is sold separately. This item can only be used with an outer barrel from the "Uni Style Fit" series. You can mix and match by combining any of the outer barrels (single colour, 3-colour or 5-colour) and inner units (gel ink, ballpoint, mechanical pencil). Ballpoint Pen Refill 0.5mm/Gel Ink Uni Style Fit Series