If you own a 6.7 Cummins diesel truck, then you may be wondering what size socket you need for the fuel filter. The answer is that you will need an 8mm or 9/16 drive socket to remove and replace the fuel filter with ease and without stripping any of the components. It is important to note that this size socket is only necessary if your particular model requires it; many other models require a different sized socket. In addition, make sure to use caution when working around hot engine parts as they can cause burns if not handled properly. When installing the new fuel filter, be sure to follow all instructions included with it and take extra care when tightening down bolts so as not to strip them or damage any of the surrounding components in your vehicle's engine bay.