Replace the old air filter in your 2001-2004 Chevy/GMC 6.6L LB7 Duramax with a Drop-In Air Filter. Find drop-in filters from manufacturers like S&B Filters, AFE, K&N Engineering, and others at XDP. Drop-in air filters get their name from their designn as most have a "drop-in" installation and simply fit inside the factory air box. Direct-replacement drop-in filters are manufactured with a paper filter media, and aftermarket filters are made with an oiled cotton-gauze, or synthetic dry filter media. Air Filters provide your engine with clean air by trapping harmful contaminants such as dust and debris before entering the intake.