A-AF25910-AI Filter, Air, Primary (QTY 1)One New Aftermarket Replacement Primary Air Filter for Cummins (Fleetguard) Engines This primary air filter replaces Fleetguard AF25910 and is designed for use on Cummins 6BTA 5. 9L turbocharged and aftercooled diesel engines. The primary air filter protects the engine intake system by filtering dust and particulate from incoming air before it reaches the combustion chamber, helping to prevent accelerated wear on pistons and cylinders in demanding