Automotive weatherseals are among the primary elements in the insulation of the passenger compartment from noise, water and dust. In addition, these profiles must integrate stringent aerodynamics and aesthetics requirements. As a result, they generally have very complex shapes and use selected sets of raw materials. The most important raw material is EPDM rubber, which imparts to the weatherseal all its elastic and sealing attributes. In references 1 and 2, the impact of the EPDM molecular structure on processing, surface quality and geometry control was investigated in detail. It was found that EPDM elastomers, which have a bimodal molecular weight distribution, provide the optimum sealing performance. Indeed, the work demonstrated that the incorporation of only small amount of very high molecular weight polymer chains significantly improves the compound elasticity and processing.