Micrometer Glass Slide for Microscope Calibration 5mm Horizontal Scale with 500 divisions -10um intervals.  

Also known as a Stage Graticule Slide.  Suitable for use with both transmitted and reflected light microscopes.  the scale is a silvered material that can be viewed as a silhouette with transmitted light or as a reflective white scale under reflected/incident light.

Micrometer Slides also known as Stage Graticules and Calibration Slides are slides with scales etched or printed on them.  The scales come in a huge variety of sizes, subdivision accuracies and patterns.  These slides are used to calibrate microscopes so measurements can be made.  Reticles are similar scales placed in eyepieces.  Both are used for measurement and counting.