This highly reflective chalk is used for marking the location of evidence found at a crime scene. The reflective chalk can be used on hard surfaces such as roads, driveways, sidewalks, etc., and can be illuminated by car headlights, flashlight, or even photoflash. Evidence can be circled, numbered, or marked with north arrows to orient outdoor crime scenes. Three marking chalks which measure 1" in diameter by 4" long are supplied in each box.