The 41210 Focusing Beam Probe Lens is used as the Lens 2 option for 77646 or 77662 focusing and imaging beam probes. This 1/2 inch (12.7 mm) diameter high purity UV grade fused silica lens has a 19 mm focal length, a 12 mm working distance, 1x magnification, and a 1.7 F/#. Lens 2 should be chosen based on the image magnification and working distance required