The new CRL Glass Chek+ Digital Glass Thickness Meter with Low-e Sensor is descended from the single pane Low-e coating detector, however the GC2001 is now able to differentiate whether the Low-e is on Surface 1 or Surface 2 of the glass. Another one of the biggest improvements is its ability to test tinted glass for low-e presence and their newest coatings that have been introduced in the past few years. This unit is capable of testing the thickness of single or double pane windows. Simply press the Glass-Chek Meter against a single lite of glass, or a dual lite window assembly, push the button and hold it until the measurements are digitally displayed. The thickness of each lite of glass, the air space, and the overall thickness of the unit will simultaneously appear on the two-line liquid crystal display. Unit can be read in decimal, fractional and metric. For best results, clean the window prior to testing. Uses one 9V DC battery (included).