Abstract: An elongated electrically insulating support structure, for use by itself as an electrical insulator or for use as a strength member in a composite electrical insulator made of fiberglass-reinforced resin, comprising a central cylindrical body and ends having the shape of solids with surfaces of revolution with axial symmetry, having diameters larger than the diameter of the central cylindrical body, with which they are radiused without solution of continuity, i.e., connected without and discontinuity, wherein the central cylindrical body and the ends consist of superimposed and crossed layers of glass filament impregnated with thermosetting resin, wound around a cylindrical element with a helical winding angle smaller than 90.degree..