Model Compatibility: Fits KLX250 D, KLX250ES, KLX250SR, KLX300R, and KLX300-B motorcycle models as specified in the title. Part Number Match: Replaces part number 21066-1093 for voltage regulator rectifier function on compatible KLX models. Functional Purpose: Restores voltage regulation and AC-to-DC conversion functionality required for motorcycle electrical system. Installation Scope: Designed as a direct-fit replacement for the voltage regulator rectifier on listed KLX motorcycle models. Application Specificity: Intended for use as a voltage regulator rectifier in the specified KLX250 and KLX300 series motorcycles.