RotopaX 2 Gallon DEF ContainerRunning a modern diesel truck with a Selective Catalytic Reduction system means DEF is just as essential as fuel and just as easy to run low on in remote areas where it is not stocked at every gas station. The RotopaX 2 Gallon Diesel Exhaust Fluid Container gives you a mount ready DEF reserve that integrates directly into your existing RotopaX setup, keeping two gallons of DEF on board and accessible whenever you need it. This is the original DEF