This disclosure relates to olefin polymerization catalysts and compositions, their manufacture, and the production of polyolefins using specific catalyst compositions, including the use of chain shuttling agents in the olefin polymerization process. Specifically, this disclosure provides for dual headed and multi-headed chain shuttling agents (CSAs or MSAs) and for their use in preparing blocky copolymers. By controlling the ratio of dual-headed and multi-headed CSA sites to mono-headed CSA sites, a blocky copolymer can be provided having properties such as a narrow molecular weight distribution and/or improved melt properties.