Roller Sets with Thrust Washer: Uses a fully rollerized, needle-bearing, Torrington-type thrust bearing to futher eliminate engine block damage and operating friction. These sets install with no block machining and should be used only in conjunction with cam button spacers to eliminate camshaft end-play. Pro-Series Steel Billet, CNC Machined Sets: Offer the precision, strength and accuracy of billet steel, CNC machined camshaft and crankshaft sprockets with the strength, friction reduction and wear resistance of a premium quality, double-row, roller timing chain. The billet steel crankshaft sprocket features nine separate keyway locations, providing up to eight degrees of advance or retard. Thrust washer included.