Micrometer are widely used in various engineering settings for measuring thickness of blocks, diameters of shafts, and depths of slots, calculates even smaller dimensions than the vernier caliper. Next to the caliper, the micrometer is the most frequently-used hand measuring instrument. Micrometers are made in various sizes and shapes, depending upon the purpose for which they are intended. Some micrometers are graduated to measure in thousandths of an inch, while others will measure as close as ten-thousandths of an inch. Other micrometers are able to measure in hundredths of a millimeter.