Features:

1. Compact in size
2. Very handy to use
3. It measures 2, 3 and 4-blade prop rpm
4. It shows 4 digits in a 0-32000 rpm range
5. It comes with a replaceable 3V 220mAH LITHIUM Battery
6. There is an auto shut-off function (no signal detected in 120 seconds)
7. When the LOW BATTERY icon is on, the battery needs to be replaced
8. It won't waste any electric power when the TACH is not in use.

Not recommended for measuring rpm of helicopter blades. The correct tool for this is the Model Avionics Sky Tach or Opti Tach.