Tombow Mono Graph Shaker Mechanical Pencil 0.5mm, Lime Green Body, R3 (SH-MG51) Mechanical pencil + Holder eraser "Tombow MONO" Core Diameter is 0.5mm. Core appear when you shake vertically pen "fure knock" deployment. Eraser out by turning the black ring at the top. Eraser refill is er-mg.