The quality of the eraser and the use of the correct eraser are critical for optimal results. Essentially, two different materials are used to make erasers: rubber and plastic. All rubber erasers and the majority of plastic erasers manufactured by Faber-Castell are PVC-free. Faber-Castell PVC-free erasers do not contain harmful plasticizers such as phthalates. The balanced blend of plastics ensures a soft and streak-free removal. The blister card includes four additional erasers for use with Poly Matic mechanical pencils.