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. Adjustable double hole car spark plug tester detector Ignition Plug Analyzer Diagnostic Tool.

Brand: Unbranded
Features: Double Hole Detector
Type: Spark Plug Tester
Vehicle Type: Passenger Vehicle
Volt: 12 Volt
Warranty: 2 Year
working frequency: 0 to 6000rpm