A Metal Oxide Varistor or MOV is the blue or orange-colored circular component that you can commonly spot on the AC Input side of any Power Supply Circuit.
TDK Corporation has presented B7221P2*, a compact S14 AdvanceD-MP series of metal oxide disk Varistors that features smaller dimensions with the same excellent performance as compared to S14 types.
A Metal Oxide Varistor (MOV) is a protection component used in power supply circuits that is powered directly from AC mains. It is used to protect the circuit from high voltage spikes by varying its resistance.