An air induction system that combines a soft, elastic sealing component with a hard, polypropylene core was specified by BMW for its 5-Series (E39) models. Using 3-D sequential blow molding, Santoprene thermoplastic rubber from Advanced Elastomer Systems, L.P. is molded with a hard polypropylene/glass-fiber material (PP GF20) This process has allowed BMW to realize significant cost savings vs. air ducts previously processed using thermoset rubber, copolyester, and polypropylene.