Features and Benefits: Operated between 3 to 28 volt No wire or clip needed while diagnosing polarity Made of rugged chrome metal Contains LED and buzzer indicator Includes long-life alkaline 23A batteries Safe for 6 and 12 volt systemsThis unit does not require ground wire or clip and is safe with ECM`s sensors transducers airbags computers etc.. Its special designed V-tip needle allows safe piercing and prevents side-slipping when piercing wire`s insulation. V-tip can be removed to test hard to reach places.