This high-quality micrometer feature a smooth-bore unthreaded mounting shank for use with slip-in, clamp style mounts. The 9351 High-Resolution Micrometer style adjustment screws has 1/4-100 threads to give you finer resolution than conventional micrometers (typically 40-pitch threads). Easy-to-read rulings are marked in 0.0001 in. increments.  These micrometers are also available on all our standard mirror mounts.