ESR240 is a modern high quality regulator/rectifier which replaces both the original rectifier bridge on the 1970-1979 Honda CB four-cylinder models, as well as the mechanical regulator. Both these units are replaced with this single modern solid state regulator/rectifier. Our ESR240 offers a much more stable voltage output at the battery compared to using the outdated OEM components. Like all other regulator/rectifiers and stators manufactured by ElectroSport we offer ESR240 with a full one year warranty. ESR240 fits: CB400F, CB500F, CB550F, CB550K, CB750F, CB750K, which are all models with a single overhead camshaft. It is designed to be a plug in replacement for these models.