Racing inspired small design, works on the inner battery. Multiple features including: tachometer, thermometer, engine running hour, MAX record and RPM/temperature alarm functions. 0-20000 RPM range (100 RPM resolution). 5000-20000 warning setting range (100 RPM resolution). 99.999h total hour meter range, resets automatically after 99.999h. 0-250 °C (32-482 °F) maximum temperature record with an effective temperature range of -10-60 °C. Includes back light dimming functions.