The X-Checker was the first and remains the only complete calibration aid for SEM/EDS Systems. Each X-Checker comes with manganese to measure full width at half max detector resolution, aluminum and copper to perform spectral calibration, and carbon to monitor calibration at the low end of the spectra for thin window detectors. You also get two grid sizes for checking the accuracy of your image analysis software and an easy test for monitoring the amount of vacuum pump oil contamination on your detector window. With: manganese, aluminum and copper, carbon, a fluorine source.