RQ-HM011F is a Self-powered Hour Meter Tachometer, contains hourmeter, tachometer, programmable maintenance reminder, user shutdown and battery saving function. Mower RPM Gauge----3 selectable engine firing patterns to keep RPM value more accurate;RPM measurement range: 0-20000RPM,10 RPM accuracy,refresh rate:0.5s. Wide Application----Small Gasoline Engine RPM Gauge Meter is suitable for gas engine 2 stroke 1 cylinder/ 2 cylinder, 4 stroke 1 cylinder/2 cylinder/4 cylinder. Resettable Hourmeter----Keep track the total hours of engine use(TOT) and service intervals(SVC); TOT hours range: 0-99999H,can be reset;SVC timer range: 0-9999.9H,can be turn OFF. Battery Saving---- CR2450 Battery capacity will be kept in good condition with insulation sheet before using or during transport; Replaceable battery compartment and LCD shutdown also can extend the lifetime in vacant time. Easy Installation----The meter comes with a cord long enough that you can install it where it makes the most sense for you and it attaches with velcro to the mower. Data Storage----User data will be retained after display shutdown or battery replaced,Don't worry about the historical data being forgotten, use it with peace of mind.