The Autool Spark Plug Tester, No. SPT360, is a digital high frequency tester for testing the performance and strength of spark plugs with a frequency up to 9,000 rpm. It's compatible with all crankshaft engine and motorcycle spark plug testing among the market. With five testing holes, users can test five spark plugs at the same time, simulating read speed and digital control. The unit is easy to use, simply insert the new spark plug in the standard test hole and old one into a test hole. Then, plug the power adapter into the rear of the power port. Next, turn on the power switch and press the up and down buttons to adjust the operating frequency.