Abstract: A spacer for insulating glazing units is presented. The spacer has a polymeric main body with features that include a first pane contact surface, a second pane contact surface, a first glazing interior surface, a second glazing interior surface, an outer surface, a first hollow chamber, and a second hollow chamber. A groove to accommodate a pane is formed between the first glazing interior surface and the second glazing interior surface, with the first hollow chamber being adjacent the first glazing interior surface and the second hollow chamber being adjacent the second glazing interior surface. Lateral flanks of the groove are formed by walls of the first and second hollow chambers.