For simultaneous two-axis measurement, the 160 series coordinate optical micrometer literally adds a another dimension to precision alignment. Two optical flats are mounted in an aluminum housing so that their axes of rotation are at 90 degrees ±15 arcseconds. This allows you to monitor two dimensions simultaneously. Many types of bore analysis jobs typically require this type of dual dimensional control. Fits all Brunson transits. This unit is in excellent condition. Follow link below for additional photos and info!