An extrusion composition containing at least one resin selected from the group consisting of polypropylene homopolymers, polypropylene random copolymers, and polypropylene impact copolymers. The extrusion composition also contains at least one phosphate ester-based nucleating agent provided in the composition at a use level of between about 0.01 and 0.15 parts by weight, in relation to 100 parts by weight of the resin. The extrusion composition also contains at least one co-additive selected from the group of poly(ethylene glycol) and copolymers containing segments of ethylene oxide, where the co-additive has a number average molecular weight of about 300 or more, and where the use level of the co-additive is about 0.005 parts by weight or more. The extrusion composition further contains a metal salt of a fatty acid at a use level of between about 0.01 and 0.15 parts by weight.