Larger diameter thimbles make these mic heads easier to read. Graduation .001", Range 0-.250??, Stem DIA .375??, Stem w/Clamp Nut, Spindle Face Flat, Remarks 1.140?? Thimble DIA. Mitutoyo Micrometer Head Larger diameter thimbles make these mic heads easier to read. Features include... 0-.250" Measuring Range .001" Graduations Stem DIA .375" Stem Clamp Nut Spindle Face Flat 1.140" Thimble DIA.