Make equipment last longer with this 4-in-one! Hour meter-non-erasable. Records actual running of engine. Flash Alert- alerts you to lube and change oil @ 25 hr. intervals. Extended power equipment life. Tachometer- shows engine RPMs (read up to 9000 RPMs). No battery required- triggered from the spark plug wire. For all single cylinder & most twin cylinder, 4 cycle gasoline engines.