The quality of an eraser and using the correct eraser are crucial for optimum results. Basically, two different materials are used to make erasers: rubber and plastic. All rubber erasers and the majority of the plastic erasers made by Faber-Castell are PVC-free. Faber-Castell PVC-Free erasers do not contain harmful phthalate plasticizer. Phthalates have been reported to cause several undesirable effects when exposed to the human body. The balanced plastic mixture guarantees soft and smear-free erasing. For use in Poly Matic mechanical pencils.