The factory RAM diesel fuel filler was designed without a fuel cap provision, leaving your expensive engine vulnerable to dirt, debris, and sedimentary deposits that lay on top of the factory fuel filler neck. The filler is sealed with a flap, but nothing other than this Fuel Cap will prevent the fuel nozzle from pushing in the caked dirt and letting it all fall into your fuel tank. The Billet Fuel Cap is sealed with a heavy-duty O-ring to give a snug fit while having enough wiggle room to remove it in the dead of winter with gloves. A high strength magnet capable of holding 4 pounds is pressed into the underside, allowing you to hang your cap on the fuel door hinge or other ferrous areas. Anodized green for a long-lasting finish.