ANCEL Car Spark Plug Tester Adjustable Double Hole Detector Ignition Test Tool

ANCEL SP02 Spark Plug Tester Ignition 0-6000RPM Adjustable Double Hole Detector. 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.