Features: 1.The tester is designed to test spark plug performance and ignition intensity. 2.With 2 test holes, two spark plugs can be tested at the same time, which is very convenient. 3.With indicator light, it can display the status of the spark plug more intuitively and understand better. 4.Easy to operate, plug and play, no complicated steps, convenient and practical. 5.If you suspect that any spark plug is not working properly, you can compare and test to make an accurate judgment. Specification: Item Type: Spark Plug Tester Material: ABS+Metal Color: Black Plug: US Plug 100-240V Spare Adapter Plug: EU Plug 125-250V Size: Approx. 140x80x40mm/5.5x3.1x1.6in (Due to manual measurement there may be a deviation of 1-2 mm) Application: 12V gasoline car spark plug Product Function: Spark plug tester: The dual-hole automobile spark plug tester tester has two test holes and can test two spark plugs at the same time. If you suspect that any spark plug is not working properly, you can compare and test to make an accurate judgment; What is the role of the spark plug? The function of the spark plug is to introduce tens of thousands of volts of high-voltage electricity into the combustion chamber and generate electric sparks to ignite the mixture. Use with the ignition system and fuel supply system to make the engine work normally, which determines the performance of the engine to a large extent. Spark plugs are daily consumables for cars. As the core of a car engine, the performance of the spark plug can almost directly determine the performance of the car, so you should always check the car's spark plug. Usage: test spark plug performance and ignition intensity. User Manual of Automobile Spark Plug Tester(Refer to the picture): 1. Insert the spark plug into or . If you want to compare the new spark plug and old one, place new spark plug into hole and the old on into hole . 2. Connect to power supply 3. Turn the knob clockwise. After turning on the power, the indicator light lights up, tester is now working at 1000rpm/min. 4. Continue turning knob to adjust the working frequency between 1000rpm to 5000rpm.The higher the frequency, the higher the spark plug strength.