The DM-13 Differential Micrometer offers sub-micron resolution in a unique design that achieves long range and fine adjustability in a single micrometer. The DM-13 has a 13 mm overall range with 0.2 mm fine adjustment range. It employs the same mounting bezel as our standard SM Series Micrometers, so it may be used to easily upgrade an existing instrument to provide, in most cases, a factor of 10 improvement in resolution. In effect, we have built a differential micrometer outside of a standard micrometer — a simple concept that is difficult to implement. The motion it provides is exceptionally smooth and crisp, without tightness or difficult turning. The DM-13 provides excellent linearity and absolute accuracy better than 1%, and its unique design exhibits no harmonic motion errors typical of conventional differential screws. The DM-13 is compatible with 461/462, 561/562, 423/433, 426/436, 460P, 460A, 401/406, RS and GON Series Stages as well as many modular optical mounts.