Abstract: Vulcanizable polymeric compositions comprising certain rubbery polymers or polymer blends, a zinc dimethacrylate adjuvant having a surface area of from about 3.7 to about 5.4 m.sup.2 /g or more and a peroxide curing agent are provided. Polymeric compositions which contain 25 parts by weight or more of the zinc dimethacrylate adjuvant per 100 parts by weight of rubbery polymer in the absence of reinforcing fillers exhibit excellent strength and hysteresis characteristcs when cured. The surface area of the zinc dimethacrylate adjuvant along with its method of preparation are extremely important factors in the excellent properties obtained when polymeric compositions containing the adjuvant are cured.