It is a high-frequency digital spark plug tester with a maximum speed of 9000 rpm. It is compatible with all crankshaft engines and motorcycles and can test up to five spark plugs at once. How to operate the device: 1- Insert the new spark plug into slot 1, and insert the old spark plug into slots 2345. 2- Insert the power adapter into the power port 10 on the back of the host device, and the indicator light will illuminate. 3- Turn on the power switch and press the up and down buttons to adjust the working frequency. The higher the frequency, the stronger the spark plug. 4- The higher the frequency, the stronger the spark plug. 5- Insert the spark plug, then turn on the power and adjust the frequency to quickly assess the condition of the spark plug. Device functions: 1- It can test 5 spark plugs at the same time (one standard spark plug, and 4 test spark plugs). 2- For long spark plug terminals. Compatible with crankshaft engines and motorcycles. 3- High-definition display with real-time rotation speed adjustment to ensure accurate test results. 4- The higher the frequency, the stronger the spark plug. 5- Insert the spark plug, then turn on the power and adjust the frequency to quickly assess the condition of the spark plug.