It has a powerful timing system, RPM measuring system as well as some other function design. Timing System Including: accumulating total running hours TOT, recording partial running time PAr,Partial timer is resettable, etc. RPM Measuring System Including:measuring current engine RPM,recording MAX RPM 5s after engine stopped, RPM refresh rate 1S ,etc Design Including: easy installed,waterproof Rate IP68,etc. This tach hour meter record gasoline engine's total running hours and partial time by the induction from spark plug cable.The hour meter shows total hours and partial time accumulated. Partial timing can be viewed and reset . Model Name: HM016R Item Weight: 65g Special Features: hour meter/timer/counter It can work on most 2 or 4 stroke gas engine. The tach hour meter shows current RPM's and total running hours when the engine is running. RPM accuracy is 10RPM. Compared with the tachometer with pointer, it displays RPM more accurate. What's more outstanding is that the tach hour meter can display engine's MAX RPM within once working period 5s after engine stopped. This can be used on top of the tachometer at different gasoline engine and machines. It is the rev counter for Paramotors, Micro-lights, Marine Engines - Inboards and Outboard. Also use for Pumps, Generators, Mowers, Model Boats, Motor Cycles, Scooters, Cleaners and Chainsaws. colour: black Material: plastic size: 6.8 x 3.2 x 1.8cm Package Contents: 3 X Digital Tachometer 3 X Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.