The 190 optical micrometer translates the line of sight laterally with an accuracy of ±0.0005″ using an optical flat. The cast aluminum housing has a 1.655″ opening to fit the telescope barrel of all Brunson optical tooling transits and levels. Adapters are available which allow this micrometer to be used with a variety of theodolites as well. Any of four machined slots in the housing (located at the 12, 3, 6, and 9 o’clock positions) fit over a locating pin on Brunson telescope barrels for quick and accurate indexing of the micrometer to a horizontal or vertical position. A precision glass window acts as a dust cover to protect the optical flat inside. Refer to the table below for descriptions of the various models in this series.