DuraWRX Diesel Exhaust Fluid (DEF) Header Assembly for Freightliner Cummins 6-Bolt 18" Tank Interface with Digital CANbus Level Sensor is a replacement DEF tank header engineered to restore accurate DEF level detection and maintain emissions control system reliability. This header integrates a solid-state, digital level sensor and heater-ready design with a 40-micron in-tank filter to manage contamination and sensing consistency. The unit mounts to the 6-bolt tank interface and includes the factory-style electrical connector employed on many Freightliner chassis with Cummins engines. By providing a direct-fit header height of approximately 18" and industry-standard suction and return ports, the assembly replaces worn or failed tank heads that cause erroneous level readings, lamping, or system derates. In fleet operations, returning a vehicle to correct DEF level reporting reduces diagnostic time and repeat service events caused by intermittent or failed level feedback. The integrated filtration and sensor technology minimize the chance of sensor fouling from particulates in DEF, while the digital CANbus interface delivers a clear electronic signal to the vehicle control system, simplifying fault isolation. Technicians benefit from an OE-style mounting interface and connector type that align with factory installation practices, cutting installation time compared with adapter solutions. Specified for service on Freightliner chassis with Cummins-equipped 6-gallon DEF tanks, this header supports repeatable level measurements that help avoid unexpected SCR derates and lost revenue due to out-of-service vehicles. Field replacement of a failed header assembly restores dependable tank monitoring and contributes measurable reductions in vehicle downtime and diagnostic labor for routes reliant on compliant emissions operation.