Spark of Genius: The engine spark tester lets you know right away if your spark plug is producing electricity; Get feedback on the consistency and strength of the spark Fits Like a Glove: Adjust your ignition spark tester as needed; Use the threaded adjustable rod that connects to the grounding clamp Keep Things Clear: An easy to read voltage gauge inside the tester lets you know if your spark plugs are strong enough to keep running; Always have up to date information about your spark plugs Multipurpose Power Tester: Use the spark plug tester for whatever you need; Find the misfiring or inactive spark plug so you can repair things quickly and with relative ease Product Details: Adjustable ignition spark tester checks the strength of electricity generated by ignition spark plugs; Adjusts to check systems up to forty thousand volts