Select the mortar and pestle that has the right characteristics and price for your application. Mortar and pestle sets come in a variety of different materials of construction. Consideration should be given as to whether what is being used currently is indeed the "right" choice given the lower limits of detection possible with modern analytical instrumentation.
For the calibration of optical measuring instruments including all light microscopes. These high quality stage micrometers are used for routine calibration of a variety of optical measuring instruments. For the professional light microscope user or researcher, these are the ultimate calibration standards for their light microscopes.