[Working principle]: The working principle of automotive spark plug tester is to test the spark plug performance and ignition strength by simulating the actual work of the engine.This tester is used to test spark plugs (12 mm diameter) for 12V gasoline vehicles, motorcycles, lawn mowers, garden , scooters, snow blowers, boats and so on [Dual Hole test and time saving]: Two spark plugs can be tested at the same time.Insert the new spark plug and the spark plug to be tested into the spark plug socket.By comparing the working performance of the two spark plugs, it can be intuitively determined whether the spark plugs need to be replaced [Adjustable operating frequency]: Spark Plug Tester Dual Holes operating frequency range is: 0-6000 rpm, and the frequency can be adjusted by turning the button.The higher the frequency, the greater the energy output used to test the ignition performance of the spark plug [Easy to operate]: First, just plug the spark plug into the socket, then put the safety cover, connect the power supply, and finally set the working frequency of the tester.(Note: For your safety, please unplug the spark plug after turning off the tester) [ Transparent Safety Cover Design]: In the spark plug area there is a protective cover on it so that accidents do not occur. Transparent protective cover also allows visualization of test results. Variable RPM to know exactly where your plugs are failing. Made of material for durability and heat resistance. Do not open the cover until the test is complete Plug Type: US Plug, it applies to Canada, India, Mexico, Thailand, Taiwan, the , the Philippines and so on. Voltage: AC100-240V Colour:As Shown Material:Metal Package Contents: 1set * plug tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.