the Co-Ax Indicator provides a simplified method for centring a workpiece or fixture on horizontal or vertical machines. Ecternal or internal diameters-also with NC.EDM. Indicator dial remains stationary while the machine spindle rotates. Length:6-7/8 174.63mm. Feeler Ball:1/8" dia. 3.18mm dia. Measuring Range:1/4" axis offset 635mm. Initial positioning: within 7/16" diameter 11.11mm circle of true location.