Ensuring you are Ready for the Road Ahead , the Dorman Diesel Exhaust Fluid (DEF) Filter successfully removes contaminates and crystals from the diesel exhaust fluid before it is injected into the exhaust stream. Protect your selective catalytic reduction (SRC) system while it works to reduce the vehicle’s environmental impact. Dorman has a distinguished reputation in the heavy duty truck and trailer aftermarket, manufacturing a variety of parts for a complete repair. Through advanced engineering, Dorman successfully checks into today’s most common failures to figure out the why, ultimately delivering modern solutions that not only match OEM parts, but solve known issues. FleetPride is your First Click in Heavy Duty .