VICTORY BLUE Diesel Exhaust Fluid DEF is a mixture of 32.5% high purity synthetic urea and 67.5% deionized water that is used in Selective Catalytic Reduction(SCR) systems on diesel engines. DEF is the primary ingredient used help convert NOx to harmless nitrogen and water. It is stable, colorless, non-flammable, non-toxic and is classified as minimum risk for transportation. VICTORY BLUE conforms to the ISO-22241-1 specification for DEF, is API registered and meets or exceeds OEM specifications.