Metal Oxide Varistor (MOV) is also known as Varistors that stands for variable resistors.
Varistor are voltage dependent, nonlinear device which have an electrical behavior similar to back-to-back zener diodes.Varistor is used to protect a circuit from high voltage surges. When a voltage surge exceeds a specified voltage (varistor voltage), the varistor suppresses the voltage to protect the circuit.
Advantages and Features:

1. High Energy Dissipation Capability
2. Fast Response Time
3. Stable Clamping Voltage  
4. High Voltage Endurance 
5. No Freewheel Current
Models:
05D, 07D, 10D, 14D, 20D