Features 1. The dual-hole car spark plug tester has two test holes, allowing you to test two spark plugs simultaneously. This enables comparison testing for accurate diagnosis if a spark plug is suspected of malfunctioning. 2. Tests spark plug performance and ignition strength, compatible with 12V gasoline vehicle spark plugs. 3. Adjustable dual-hole spark plug tester serves as a diagnostic tool for evaluating spark plug operation. 4. Purpose: To test spark plug performance and ignition strength. 5. Application range: 12V gasoline engine vehicles. User Manual: 1. Insert the spark plug into tester hole 1 or 2. For comparison between a new and old spark plug, place the new spark plug in hole 1 and the old one in hole 2. 2. Connect the device to a power supply. 3. Turn the key switch clockwise to activate the tester. The indicator light will illuminate, indicating the tester is operating at 1000 RPM. 4. Continue turning the key switch clockwise to adjust the operating frequency from 1000 to 6000 RPM. Higher frequency results in stronger spark intensity. Specifications Material: ABS Color: Black Size: 16.5 x 10.5 x 7 cm Weight: 200 g Package Includes: 1 x Spark Plug Tester 1 x Power Adapter