Description_x000D_ General description_x000D_ Pair of PhEur 2.2.24 certified polystyrene calibration films. One film is 38 microns and is provided with certification of traceability to seven (7) PhEur 2.2.24 frequencies. The second film is 76 microns and is provided without certification. Both films are mounted on 2" x 3" cardstock holder with a 19mm aperture for mounting in the universal slide holder in all instruments. Includes instructions for two (2) film ordinate calibration and storage case.