Ensuring you are Ready for the Road Ahead , the Fuel Tank Accessories Non-Locking Fuel Cap keeps your diesel fuel from being contaminated by outside environment factors, such as dirt and dust. To make sure this gas cap replacement is the right fit for your truck, always measure the inside diameter of the fuel cap. This fuel cap gives you the confidence both your fuel tank and fuel system remain protected. FleetPride is your First Click in Heavy Duty .