Function: If you suspect the spark plug is not working properly, test the performance of the spark plug by simulating car ignition to decide whether to replace the spark plug. for spark plug tester Two Test Holes: The Two Hole Automotive Spark Plug Tester Detector has two test holes, which can test two spark plugs at the same time. You just need to put a new spark plug and a spark plug to be tested into the test holes respectively. Can quickly and accurately test spark plug performance. Scope: This spark plug tester detector tests the performance and ignition intensity of spark plugs and is suitable for spark plugs in 12V gasoline vehicles. Original Standard: This spark plug tester detector is professionally manufactured and designed in strict accordance with required standards, with stable performance and high reliability. Adjustable: The operating frequency of this spark plug tester detector can be adjusted between 1000 rpm and 5000 rpm. The higher the frequency, the stronger the intensity of the spark.