MOV-20D391K is a 20 mm radial leaded metal oxide varistor that protects against overvoltage transients such as lightning, power contact, and power induction. This device features a nominal varistor voltage of 390 V with a maximum continuous voltage rating of 250 V (r.m.s.) and 320 V (d.c.), providing robust surge protection with a fast response time of 10–25 ns. The varistor exhibits high current handling capability with a maximum peak current of 6500 A (8/20 µs waveform) and maximum energy absorption of 180 J per surge event, along with a typical capacitance of 1200 pF at 1 kHz. The device operates reliably across a temperature range of -40°C to +105°C and is RoHS compliant with UL 1449 agency listing. MOV-20D391K is commonly used in power supplies, power systems, line voltage protection, telecom systems, and white goods/appliances where transient overvoltage protection is critical.