Hour Meter : A small tool can help you to keep tracks of gas engine total and partial running hours; Perform the regular maintenance tasks(eg.air filter and oil change) to determine when the time is due. Tachometer: Display the engine current RPM value and highest RPM hit since engine started to adjust the idle speed; Various of engine firing patterns can be chosen for RPM accuracy correction; can set Alert RPM to protect your engine Easy to set: wrap the singal wire wrap spark plug 4-5 turns and fasten it. Then set tachometer according to engine type. The product can working. Two ways to installation: The product allows for 2 ways to installation(3M adhesive velcor and Screw installation). You can choose suitable ways according to your surface. Other Features: Black light, Adjustable RPM refresh rate,Waterproof IP65, Long service life with CR2032 Battery, widly application, Reliable after-sales group and technical support.