ESR438 has been designed specifically as a high quality regulator to replace the not-so-reliable OEM regulator/rectifier on the VFR800 between 2002-2007, as well as the RC51 between 2000 and 2006. We used our latest generation power circuitry and installed it in a highly efficient heat sink design. The resulting ESR438 offers a stable voltage output to your battery, and a much cooler running housing which dramatically improves reliability. A great improvement over the stock unit. Our ESR438 is supplied with a full one year warranty.