The Model 497 film thickness gauge serves two purposes: It can be used to directly measure the thickness of sheets, plastic film, cartons, papers and other laminates. The second key feature is measuring the thickness of coatings on the aforementioned thin substrates. Magnetic or electrical thickness measurement methods cannot be used for non-metallic substrates. A differential measurement using this device is the only non-destructive method available. Only the measurements on Leneta film for the chafe test according to DIN 53 778 T2 and on black and white contrast boxes for colour measurements and opacity determinations are considered to be particularly critical usages for this device.