The FTR20D511K is an FTR-branded electronic part, a varistor with rated voltage of 415V to 845V, 6.5KA pulse power, and 10mm P rohs containing package. It is designed for through-hole mounting and is RoHS-compliant, helping ensure best-in-class performance in stringent applications. It has both advantages and disadvantages. Advantages of this part include high voltage protection in both AC and DC applications and its wide working temperature range of -40°C to +115°C. Disadvantages include vulnerability to over-voltage conditions in the unprotected side, when used as a surge diverter.