The 6150 multiple paired-line glass target, with horizontal and vertical displacement scales, is mounted in a hardened and ground-stabilized steel ring. It is centered within 0.0005" with respect to the ring's outside diameter. This target is useful when you need to measure or estimate deviations from a line of sight which exceed an optical micrometer's range. The graduations on the target act as "scale" and may be read using the optical micrometer as a vernier in much the same way that optical tooling scales are read.