An insulator typically comprises an insulating core that extends between two electrodes which are maintained at significantly different electrical potentials. Insulators have been made with various materials. High voltage electrical insulators for use at voltages in excess of about 1 kV, and typically at 24 kV, can be made from porcelain, glass fibre, or solid polymeric material. Porcelain has good electrical properties but is heavy and brittle, thus having low resistance to vandalism. Glass fibre rod impregnated with an epoxy resin is of lighter weight but generally has inferior electrical performance to porcelain in outdoor applications, or must be environmentally sealed. A composite insulator comprises a structurally strong core or rod typically made of fibreglass, a series of electrically insulating sheds, and two metal end fittings crimped onto the exposed ends of the electrical insulator. Electrical polymer insulators are used in power transmission and distribution systems to provide mechanical support for the conductors and provide electrical insulation between the high voltage conductors and grounded tower structures. Polymer insulators are each constituted by covering the outer periphery of a core member made of an FRP with shed portions made of silicone rubber. Solid polymeric material, which combines the advantages of light weight and good electrical performance but has poorer load bearing properties. Polymeric tubing and/or sheds (annular extensions) may be added to porcelain or glass fibre rods, or incorporated into polymeric insulator, for enhanced performance. High voltage suspension insulators are used to suspend power transmission lines from overhead supports on poles and towers. Suspension insulators used to be made of strings of porcelain insulators having a size and shape required of that material to provide the necessary mechanical strength, dielectric strength and creepage distance. Nowdays, most suspension insulators are formed of a fiberglass reinforced polymer rod and an external protective housing forming the weathersheds. The weathershed housing is usually made of an elastomer or an epoxy material. Elastomer or epoxy weathershed housings are designed to protect the fiberglass reinforced rods from weather and electrical activity.