Prevent sand, mud, and dirt from damaging the air filter in your 2004.5-2005 Chevy/GMC 6.6L LLY Duramax with a Pre-Filter. Find the right pre-filter for your intake system by matching up your filter part number, or by using the filter dimensions. Pre-filters are manufactured from a breathable material that lets air through while blocking large debris and contaminants. Pre-Filters are installed over top of your air filter and serve as another layer of protection from airborne contaminates that could otherwise damage your filter, air intake, or engine. Pre-filters from AFE, K&N Engineering, Banks, and others are all available at XDP.