Extech CG104 Coating Thickness Tester Ferrous Non-Ferrous Substrates measures the thickness of non-ferrous and ferrous substrates via non-destructive means. The Extech CG104 features an intuitive menu system, a backlit and reversible display, the ability to store and recall up to 255 readings, automatic recognition of non-ferrous and ferrous substrates, programmable high and low alarms, and more.