Replace the old air filter in your 2004.5-2007 Dodge 5.9L Cummins with a Drop-In Air Filter. XDP carries drop-in air filters from manufacturers like S&B Filters, AFE, K&N Engineering, so you can find the best one to meet your vehicle's needs. In most cases an oe-style drop-in air filter will be made with paper filter media, where an aftermarket air filter typically features a synthetic media, or a cotton gauze design that may be dry or oiled. Drop-in air filters are aptly named as they have a "drop-in" installation that allows them to fit inside of your factory air box. The air filter in your vehicle serves as the first line of protection against harmful airborne debris that can damage your engine.