Rheem Complete Combustion Assembly SP21001B Genuine OEM. This is a Genuine OEM Rheem part. Basic InformationPart Name: Water Heater Combustion AssemblyManufacturer: RheemCategory: Water HeaterPrimary Function: Provides the burner and blower system that ignites and regulates combustion in the water heaterIn... - Rheem Complete Combustion Assembly SP21001B Genuine OEM.