Abstract: It is possible to improve significantly the optical performance of diacetal or DBS-based nucleating or clarifying agents using a co-additive. Haze is a measure of the lack of clarity in a thermoplastic or plastic material. A low level of haze is usually quite desirable, and nucleating/clarifying agents are designed to reduce the degree of haze in a plastic or thermoplastic material. A co-additive may be used in connection with a nucleating/clarifying agents in a polymer or copolymer to achieve even greater results in terms of improved clarity (reduced haze), or in terms of a higher crystallization temperature (Tc) of the polymer. A method for reducing haze in polymer articles using a co-additive composition in addition to nucleating and clarifying agents is disclosed.