Dual Hole Car Spark Plug Tester Detector have two testing holes, you can test two spark plugs meanwhile and and if you suspect any spark plug works improperly you could compare and test to make accurate judgment. Adjustable double hole car spark plug tester detector Ignition Plug Analyzer Diagnostic Tool Car Spark Plug Tester Detector with Dual Hole Advantage: Dual Hole Car Spark Plug Tester Detector have two testing holes, you can test two spark plugs meanwhile and and if you suspect any spark plug works improperly you could compare and test to make accurate judgment. Usage: Test spark plug performance and ignition strength Application Range: 12V Gasoline vehicles car spark plugs Car Spark Plug Tester Using Note: 1. Please Turn Off Power before you place spark plug 2. The Spark Plug Tester is a high-voltage detector, so do not touch spark plug with hand at work to avoid danger. Car Spark Plug Tester User Manual: 1.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 2.Close up the protective cover , then plug in the adaptor to the side socket , connect the tester to power supply. 3.Turn the key switch clockwise to turn on tester, indicator will light up green. 4. Continue to turn the switch clockwise, you can adjust the working frequency between 1000rpm to 6000rpm/min, The higher the frequency is set, the stronger the spark more. Product Parameters: Power Adapter: Input 100-240V AC / Output 12V 1A DC Plug Type:EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on The appearance of the power adapter is random due to different batches. Don't accept the specified, which does not affect the use Voltage: AC100-240V Colour:Photo Color Material:ABS Package Contents: 1 x Spark Plug Tester 1 Adapter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.