Highly effective processing aid made from EPM rubber for rubber compounds based on EPDM, IIR, NBR and CR rubber. The incorporation and distribution of fillers and other rubber chemicals is significantly improved, so that mixing times can be reduced. In polychloroprene in particular, the mixing temperature can be lowered in many cases, reducing the risk of scorching. Haftolat behaves neutrally during sulphur and peroxide vulcanization.