Exhaust gasket ring, copper, Norton OHV singles, replace every time you remove the exhaust pipe. Cylinder head exhaust port to exhaust pipe gasket. Suits years 1935? - 1962+. OD: nominal 2inches; ID: nominal 1-3/4inches. Note: Apply anti seize (Copper Eze P-CEZE0001) to the exhaust nut EVERY time. Original Part Number: 3720; A3/166, E6842 - Exhaust pipe flange washer (cylinder head)