ITEM NAME:Car Spark Plug Tester With Adjustable Double Holes Ignition Testers Analyzer.Place the Spark Plug into tester hole 1 or 2; If you want to compare the new spark plug and old one, place new spark plug into hole 1 and the old on into hole 2. Turn the key switch 4 clockwise to turn on tester, indicator 3 will light up, tester is now working at 1000rpm/min.
