The Tombow MONO Graph Mechanical Pencils feature one of the most popular erasers in Japan, the MONO eraser. To prevent the lead from breaking and to help with precise work, MONO Graph has a 4 mm long guide pipe. They also feature an innovative shake-mechanism that allows the user to extend the lead by simply shaking the pencil. The pencils is also equipped with a lock mechanism to prevent accidental lead extension. Refillable eraser. 0.5 mm lead.