Car Spark Plug Tester Adjustable Dual Holes Engine Coil Ignition Plug Analyzer

Dual Plug Car Spark Plug Tester 12V Gasoline Ignition Plug Diagnostic Tool. 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.