An X-ray lens, typically at a synchrotron X-ray beam line. Based on information provided by Gerd Wellenreuther (DESY). Geometry of the lens Is the device symmetric? Is the device cylindrical? Orientation of the cylinder axis. The type of focus of the lens Thickness of the lens Length of the lens Radius of the curvature as measured in the middle of the lens Diameter of the lens. Number of lenses that make up the compound lens. Material used to make the lens. Gas used to fill the lens Gas pressure in the lens