Starrett, 55944, 1/2 Inch, 35/64" Plain Thimble, 0.2" Dia x 3/4" Long Spindle, Mechanical Micrometer Head 3-7/16" Long, Accurate Up to 0.0001", Flat Spindle, 0.3937" Dia x 3/8" Long Stem, Steel Measuring Face