IEC 61109:2008 applies to composite suspension/tension insulators consisting of a load-bearing cylindrical insulating solid core consisting of fibres - usually glass - in a resin-based matrix, a housing (outside the insulating core) made of polymeric material and end fittings permanently attached to the insulating core. The main technical changes with respect to the previous edition are - removal of tests procedures now given in IEC 62217; - inclusion of clauses on tolerances, environmental conditions, transport, storage and installation; - general improvement of the description of tests and addition of a new Annex C on non-standard loads.