This internal air filter element, designated CF800 by Mann-Filter, captures airborne particulate before it enters the engine intake system. It sits inside the main filter housing on the engine, acting as a secondary barrier that traps fine dust not stopped by the primary element. A clogged inner filter restricts airflow, leading to reduced engine power and increased fuel consumption. The filter is constructed to match the original housing's seal geometry, ensuring a proper seal that prevents unfiltered air from bypassing the element. On replacement, ensure the housing is clean and the sealing surfaces are free of debris.