Unfortunately, the original injectors found in 2001-2004 Duramax powered Chevrolet and GMC's had notorious failure issues. If you're one of the unlucky ones that are found needing to replace your injectors, or possibly you're upgrading to a higher displacement set of injectors, then you'll need more than just the injectors for a proper installation. This kit from Merchant Automotive includes everything you'll need to get the job done right the first time.