The Elcometer 990 Calibration Foils, also called shims, are precision thickness foils used to create a coating thickness standard on the actual substrate material, surface finish or form. Adjusting a coating thickness gauge against a foil that matches the substrate is the most convenient way to set up the gauge for the greatest possible accuracy, which matters because an incorrectly calibrated gauge produces readings that look right but are not.

Each foil of the Elcometer 990 Calibration Foils carries its metric and imperial value and a unique serial number for traceability, and foils are available individually or in sets. The Elcometer 990 Calibration Foils cover a wide span of thicknesses, from 12.5µm up to 25mm, colour coded across the range, for example purple at 25µm, dark blue at 50µm, green at 75µm, brown at 125µm, white at 250µm and black at 500µm, through to thicker grey and clear foils for the millimetre values. Precision foils have an accuracy of plus or minus 1%, and foils below 50µm have an accuracy of plus or minus 0.5µm.

Two certificate options are available for the Elcometer 990 Calibration Foils: a Certificate of Calibration, issued for fixed calibration equipment and showing readings and traceability, and an Accredited Certificate, a full UKAS traceable certificate issued by an independent calibration laboratory. Used by coating inspectors to verify and adjust dry film thickness gauges, the Elcometer 990 Calibration Foils are supplied by BAMR, South Africa's authorised distributor.