this way the hardness of the final product can be easily controlled the admixed polybutadiene preferably has a molecular weight between 1 000 to 4 000 and a viscosity of 700 to 3 000 mpa s furthermore it is advantageous when the polybutadiene has 70 to 80 1 4 cis double bonds 15 to 30 1 4 trans double bonds and 1 to 5 vinyl double bonds it has also been found advantageous to add 0 5 to 5 polynorbornene a polymer of di cyclopentadiene to the composition this improves and increases the abrasion which is particularly important for satisfactory functioning of the eraser this polynorbornene can be added in addition to the conventional inorganic fillers since polynorbornene has an especially great specific surface and therefore an extremely good capability to absorb fats and oils this makes it possible to achieve an especially fine and absorptive abrasion it is also possible to add alternatively or as a supplement relatively small amounts of factice chlorinated and or sulfurized plant oil to achieve further improvements in the abrasion and in turn the erasing properties moreover it has been found that in place of polybutadiene or in conjunction with the polybutadiene it is advantageous to add relatively small amounts of naphthenic.