In your 5.9L or 6.7L Cummins, ensuring the fuel connector tubes in your cylinder head are secure is vital to the performance of your engine. Loose tube nuts can create leaks and lead to hard starts, low power, bad fuel economy or even a no start condition all together. Replace your factory tube nuts with the Fleece Perfromance 300 Series Stainless Steel Tube Nuts. These nuts ensure a proper seal on your injector tubes and high pressure injection lines with these high tolerance tube nuts. Sold as a set of 6.