Abstract: A ceramic insulator having sidewalls, a front wall and a back wall with an outwardly extending mounting shoulder at the upper end of the front and back walls; a passageway extending between the sidewalls of the insulator to form an open interior portion within the insulator which receives a ribbon heating element and a slot in the front wall connecting with the open interior portion of the insulator for insertion of a ribbon heating element into the open interior portion; a bearing surface within the open interior portion to support a ribbon heating element; and an elongated radiused rib extending outwardly from each sidewall below the bearing surface to provide curved contact surfaces for a ribbon heating element.