WirthCo Battery Doctor Circuit and Spark Plug r is designed to instantly locate wiring problems such as bad connections, faulty or broken wires and sockets in 12 Volt - 24 Volt systems. A light will shine if the battery or circuit's condition is sound. No light will be visible if there is a short circuit or the battery is low. This high quality r includes an alligator ground clip and 3 inch metal probe with cover. The overall length is 8 inches with a full 45 inch lead wire. WirthCo has been a prime manufacturer of practical products for making life easier and safer. California Prop 65 - Warning, This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.