SPI Disc Micrometer Disc flanges on micrometer make it possible to get accurate measurements on areas not reachable with standard micrometers such as gear pitch, ribs, slot and groove distances. Features include.... 0-1" Measuring Range 0.0001" Graduations 0.0001" Accuracy 3/4" Disc Flange Diameter Painted frame with plastic heat shield Spindle dia.: 0.250" Ratchet thimble Lever lock Certificate of Calibration Furnished in fitted case