This is a Stage 2 Performance injector used in the Mack ETECH CCRS engine. It provides about a 18-20% increase over stock. The CCRS injector can be identified by the absence of a fuel return hole on the injector body-THERE IS NO FUEL RETURN HOLE CORE CHARGE: A core charge of $150.00/injector will be applied to your credit card account, if the old cores are returned within 30 days, you will get credit. Feel free to call our parts department at 800-891-8038 with any questions.