Precision measurements of internal engine parts and other critical dimensions are made with micrometers, some of which can accurately measure to within thousandths of a millimeter. These are expensive instruments, and are only recommended for those who plan to be repeatedly involved in engine overhauls or other similar work requiring detailed measurement. If such measurements are necessary on a one-time basis, a qualified machine shop can be called upon to make these measurements, particularly if they are also going to be doing the necessary machine work.