SPI Electronic Blade Micrometer This is the prefect gage for easy measuring of narrow grooves, slots and keyways. Features include... 0-1" / 0-25mm Measuring Range 0.00005" / 0.001mm Resolution Spindle & Anvil are hardened, ground, and lapped. Friction Thimble Non-Rotating Spindle Blade Dimensions are as follows... 0.030" Thick 0.256" Wide