Features: 1. The detector have two testing holes, you can test two spark plugs at the same time. 2. If you suspect any spark plug works improperly, you could compare and test to make accurate judgment. 3. It can test spark plug performance and ignition strength, and it can be used for 12V gasoline vehicles car spark plugs. 4. The dual-hole automotive spark plug detector can adjust the diagnostic tool of the spark plug analyzer. 5. You can adjust the working frequency between 1000rpm to 5000rpm/min. The higher the frequency, the better the spark strength. Specification: Condition: 100% Brand New Item Type: Spark Plug Tester Material: ABS Usage: Test Spark Plug Performance And Ignition Strength Application Range: 12V Gasoline Vehicles Car Spark Plugs Plug: US Plug Car Spark Plug Test principle: In automobile ignition system, the high-voltage ignition coil generates a high-voltage (10000 volts or more), and the spark plug diverts it form, high -tension ignition coil into the cylinder engine, spark between the spark plug electrodes will ignite the mixture. The Detector could tell the good spark plugs from the bad by the strength of the spark. Car Spark Plug Tester User Manual: 1.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 2. Connect to power supply 3. Turn the key switch 4 clockwise to turn on tester, indicator 3 will light up, tester is now working at 1000rpm/min. 4. Again turn the key switch 4 clockwise, you can adjust the working frequency between 1000rpm to 5000rpm/min. The higher the frequency, the better the spark strength. Package List: 1 x Spark Plug Tester 1 x Power Adapter Note: 1. Please turn off power before you place spark plug. 2. The spark plug tester is a high-voltage detector, so do not touch spark plug with hand at work to avoid danger.