This standard applies to lampholders designed with a barrel thread for shade holder rings designed to keep attachments to lampholders in place. It also covers barrel threads for shade holder rings. Attention is drawn to lampholder safety standards IEC 60238, IEC 60400, IEC 60838-1 and IEC 61184 which cover all aspects of lampholder safety and to the luminaire standard IEC 60598-1 which contains information for luminaire design.