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 systems This 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.