Quickly identifies the two most common types of pulley misalignment - parellel offset and angular. Simply position the tool within the grooves of a pulley and aim its bright laser beam at an opposite pulley. Any misalignament is instantly visible. This tool is compatible to industrial V-belts drives and most suitable for serpentine belt drives. This lightweight and easy-to-user tool includes special laser enhancement eyeglasses for easier viewing in all light conditions and comes with a high-impact resistance plastic case.