Polymer SP insulator

A polymer SP insulator comprising an FRP core , a sheath having a plurality of sheds provided on outer periphery of FRP core , and metal-end-fittings crimped to upper and lower ends of FRP core , in which a flat plate for adjusting the overall length dimension after crimping the metal-end-fitting is assembled in the inner bottom of the metal-end-fitting , and the overall length dimension is uniformly adjusted by the thickness of the flat plate . Further, a stress concentration portion such as cross groove is provided in the outer bottom of the lower Metal-end-fitting , and prevents instability by deformation of flange when crimping the Metal-end-fitting . In this configuration, in spite of the structure of crimping metal-end-fittings at upper and lower ends of the FRP core, the overall length tolerance, parallelism and eccentricity can be suppressed. In order to assure the flashover distance economically, preferably, the diameter of sheds of at least highest position and lowest position is larger than the diameter of intermediate shed.