Used for measuring pavement planeness. Operated by one person along a highway, airport runway, or bridge surface. The unit detects and dye-marks high and low areas that need to be ground or rerolled. Variations are magnified 16 times on a vertical scale graduated in 1/8" increments up to 1/4". Uses replaceable bright orange aerosol marking dye. One case, (12) cans, comes with unit.