Extech cg205 coating thickness tester and calibration film extech cg204 the extech cg204 coating thickness tester uses dual technology to provide automatic recognition for ferrous and non ferrous substrates its internal memory stores 400 readings 80 direct and 320 group which can be transferred to a pc via usb for use with the supplied software supplied with 2 x aaa batteries usb cable software calibration iron calibration aluminium precision standards and pouch case extech cg204 la