The distributions of the molecular weight (MWD) and chemical composition of polyolefins can be controlled by the combination of two or more metallocenes from the knowledge of the behavior of each individual metallocene. Polyolefins with bimodal MWDs and a higher comonomer content in high molecular weight chains have physical properties suitable for advanced applications such as pipes for gas and water distributions. With conventional Ziegler-Natta catalysts, this type of polymer resin is produced only by tandem reactor technology in which two or more polymerization reactors are used in series. With combined metallocene catalysts, similar polymer resins can be produced in a single reactor. The versatility of these combined metallocene catalysts is investigated in this article.