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 outside diameter of the ring. 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.