SPI Electronic Spline Micrometer This micrometer with its carbide measuring faces is designed to help you measure diificult applications like shafts, slots, and keyways. Spline Diameters: 0.079" / 2mm Features include... 0-1" / 25mm Measuring Range 0.00005" / 0.001mm Resolution 0.00016" Accuracy 0.250" Spindle Diameter ABS / Inch / Metric Measuring Ratchet Thimble Certificate of Calibration Furnished in fitted case