HURI Fuel Valve Petcock for Generac Centurion Generator GP5500 0059390 5939 6110 Replacement parts,non original Hex cap size is 22mm (about 7/8 in) Thread size is M16 X 1.5mm (thread size about 5/8 in, thread pitch about 1/16 in) Package include 1pc petcock + 1pc HURI pocket tape Note:you could apply for a full refund if you didn't receive HURI branded pocket tape.