Merlin Lazer Glass Enviro KitMerlin Lazer TGi Toughened Glass Indicator and Merlin Low E Glass Coating Detector now available in a handy Kit with free Carry Case. Toughened Glass Indicator TGi The Merlin TGi could hardly be easier to use, simply place it on the glass to be tested then slide it across the surface while looking into the viewing window. The colour of the light reflected back from the glass surfaces will indicate instantly whether or not the glass has been toughened.