This part of ISO 12090 establishes the boundary dimensions and tolerances for series 1, 2 and 3 of linear motion rolling bearings, profiled rail guides. These bearings consist of profiled rails with carriages, which can support forces from all perpendicular directions and moments around all axes and consist of recirculating rolling elements. The internal design of these profiled rail guides is at the discretion of the manufacturer. An assembly, as specified by the manufacturer, can comprise one or more carriages on a profiled rail. Therefore, the interchange or combination of these elements can only be carried out within the limits permitted by the manufacturer.