Features 1. The dual-hole car spark plug tester detector has two test holes, you can test two spark plugs at the same time, if you suspect any spark plug is not working properly, you can compare and test to make an accurate judgment. 2. Test spark plug performances and ignition strength, suitable for 12V gasoline car automobile spark plugs. 3. Adjustable dual-hole car spark plug tester detector spark plug analyzer diagnostic tool 4. Purpose: Test spark plug performances and ignition strength. 5. Application range: 12V gasoline car automobile spark plug. 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 6000rpm/min. The higher the frequency, the stronger the spark strength Specification Material: ABS Color: Black Size: 16.5 x 10.5 x 7 cm Weight: 200 g Package Include: 1pc x Spark plug tester 1pc x Power Adapter