1. [High-quality materials]: The spark plug tester is made of high-quality plastic and metal, which is durable. Not easy to age, good toughness, balanced hardness and mechanical properties, low impact resistance, and high product quality. The flexible double-headed tool with an internal bulb can be used for many years and is interchangeable with the transparent shell. 2. [Easy to use]: You only need to connect the metal end of the tester to the spark plug coil and start the engine. When the ignition cable is intact, the indicator light will light up. Use this ignition spark tester to check the ignition system status of each cylinder without expensive mechanical maintenance. 3. [Easy to observe]: Transparent observation window, easy to observe the overlap, confirm whether it is normal, and easy to use. Just connect the tester between the spark plug and the spark plug cable. When the spark is emitted, the tester will reflect the spark and ignite the spark. Check whether the spark plug is dirty and whether the tip is damaged. 4.【Wide Application】: The engine coil tester is an essential tool for troubleshooting all internal and external combustion engines (such as cars, trucks, motorcycles, lawn mowers, chain saws, trimmers, snow blowers, generators, etc.).