The mounting concept of traditional X-ray optics technologies is illustrated in images A and B. The closed mirror shells or sectors are mounted to the support structure at individual points. In the Silicon Pore Optics technology ribs attached to the back of the mirror elements form the mounting elements (image C). These ribs dramatically increase the stiffness of the mirror elements in the critical longitudinal direction. Mirror elements are stacked upon each other in the SPO approach, forming a stiff, monolithic structure containing many mounted mirror elements (image D).