The standard acts as a guide for the application of composite insulators to overhead transmission and distribution lines. It is based on utility field experiences, results of research laboratory tests, and manufacturers' recommendations. It deals with composite insulators, which include a core, weathersheds, and metal end fittings. The core consists of resin and glass fibers. The weathersheds are of polymeric materials such as epoxy resins or elastomers and normally contain inorganic fillers.<>