Quickly identifies the two most common types of pulley misalignment - parallel offset and angular by emitting a bright laser light beam to the opposite pulley, instantly indicating the degree of misalignment This innovative drive alignment tool is compatible with all automotive serpentine belt drives with four ribs or more found on both cars and light trucks. Align serpentine belts Identify bracket problems Laser type: 650nm visible laser diode Operating time: 20 hours continuous service Battery type: replaceable lithium battery Carry case: high-impact plastic with die-cut foam insert Bungee cord: holds laser to pulley Eye glasses: enhances laser light Allen wrench: aligns laser light beam Most accurate alignment method Shows offset and angular misalignment Uses proven laser beam technology Extremely light weight, fast and easy to use One person operation