Laser Labs Tint Meter Model 100 is a hand held device that measures the amount of light that passes through a window. It measures the total amount of Visual Light Transmission (henceforth referred to as VLT) through a window and any coatings (tint film) on that window. The device was designed, as an affordable way for law enforcement officers to measure the total VLT of a window after it has been treated with aftermarket window film. The device slides over a partially rolled down window, does its calculations, and in seconds displays the readings on a liquid crystal display (LCD). Because it has its own internal light source, the meter will work day or night. Available in 1 or 2 piece.