IEC 60399 pdf download Barrel thread for lampholders with shade holder ring 1General 1.1 scope This international standard applies to lampholders designed with a barrel thread for shadeholder rings designed to keep attachments to lampholders in place. lt also covers barrel threads for shade holder rings. Attention is drawn to lampholder safety standards lEC 60238,IEC 60400, IEC 60838-1 andIEC 61184...