Quickly diagnose problems with all ignition systems,Connect the tool between the spark plug and the plug wire Normal of fire gauges as" blue and 2cm straight line,"if the ignition coil is bad when the color is red or curve Use this ignition spark tester to check the condition of the ignition system at each cylinder without going to expensive mechanics.The spark tester connects between the spark plug and spark plug wire in seconds to troubleshoot dirty spark plug connections,defective points and bad cables or connections.Connects in seconds. Colour:Black material:plastic Size:Jumping distance is about 0.8-1.5cm Package Contents: 1pcs * Spark plug tester Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.