ESR320 is a modern regulator/rectifier that replaces the OEM units on the earlier Yamaha XJ550, XJ650 and XJ900 Seca and Maxim models. This regulator is vastly improved over the poorly performing OEM regulators in these bikes due to modern circuitry and efficient heat sink design. Output voltage is stable across the RPM range and heat dissipation is superior resulting in a very reliable unit. ElectroSport offers a full one year warranty on this ESR320 regulator.