SPI Electronic Deep Throat Micrometer Features Include... 0-1" / 25mm Measuring Range 0.00005" / 0.001mm Resolution 0.0002" / 0.005mm Accuracy 12" Deep Throat Flat Carbide Faces on Anvil & Spindle Enamel finish frame. Ratchet Stop. Spindle Lock For sheet metal and similar applications Inch/Metric absolute and relative measuring conversion Spindle diameter: 0.250" Certificate of Calibration Furnished in fitted case