ROLLMASTER VERNIER ADJUSTABLE TIMING GEAR TO SUIT FORD FAIRLANE NA NC NF NL SOHC MPFI 3.9L 4.0L I6This Rollmaster billet steel cam gear is produced in two parts which allows the outer sprocket section to move separately and independently to the inner hub by way of elongated slots. Infinite adjustment to cam timing is possible by positioning the camshaft to the required angle then locking the socket head screws around the perimeter of the gear which clamps the entire unit together as one solid cam sprocket. The cam gear teeth are all nitrided for