This is the SenDEC (FAST-TACH) This is the FS 500 which does three functions instead of the FS 5000 that only does one. This unit has a hour meter, Job Timer and Tachometer. This is by far the most accurate and widely used Tach for RC Boating on the market and you can log the time you have on your engine. It is accurate up to 20,000 RPM. Use this for tuning or for maintenance of your engine to make sure everything is in top shape.