Brand new Regulator Rectifier for your Yamaha XS400. This unit will replace both the Regulator and Rectifier. Since there is no specific mounting spot for this unit, you will have to determine the best mounting spot for your unit. In the 6-gang plug on the unit we offer will plug into the wiring harness where the original unit did. In the 3-gang connector on the unit we offer will plug on the harness where the original unit did. The wire colors in the unit may not match OEM. There are extra regulator connector and terminals supplied in case the factory unit requires opposite end plugs. Anti-gravity batteries are not recommended to be used, as they have non standard charge points.