Features: brand new and high quality Dual Hole Car for Spark Plug Tester Detector hve two testing holes, you can test two spark plugs meanwhile and and if you suspect any for spark plug works improperly you could compare and test to make accurate judgment. User Manual:1. Insert the for spark plug into the test hole 1 or 2; if you want to compare new spark plugs and old spark plugs, put the new for spark plug in the hole 1 and the old hole 22. Connect the power3. Turn on the for key switch 4 clockwise to open the tester, the indicator 3 will illuminate, and the tester is now working at 1000 rpm / min.4. Turn the for key switch again to adjust the operating frequency to -5000 rpm / min. The higher the frequency, the for stronger the spark intensity. Using Note: 1. Please Turn Off Power before you place for spark plug. 2. The for Spark Plug Tester is a high-voltage detector, so do not for touch for spark plug with hand at work to avoid danger. Only for 12V car Only for 12mm for spark plug. Specifications: Material: Metal+ABS Size: Approx.85x120mm/3.35x4.72in Type: EU, US(optional) Frequency: 1000-6000 RPM/min Output: 12V 1A for DC Input: 220V AC Package Includes: 1x for Spark Plug Tester 1x Power Adapter note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. 3.Only for 12V car Only for 12mm for spark plug. 4.Not for European for spark plug.