This air filter element captures airborne particulate before it enters the engine intake system. It is the inner element of a two-stage assembly, working in series with the outer primary filter to provide final-stage filtration. The element is installed inside the housing on the engine; its pleated media traps fine dust that passes the outer stage, protecting the turbocharger and combustion chamber from abrasive wear. A clogged inner element restricts airflow, causing a drop in engine power and increased fuel consumption. The manufacturer specifies this element to match the housing's seal geometry and bypass-valve cracking pressure, ensuring the filter system maintains proper restriction levels. When replacing, inspect the housing seal and seat the element fully before closing the cover.