The ULTIMATE in double roller timing sets! The difference is accuracy. No more problems degreeing cams because these billet timing sets have nine keyways (2,4,6,8, advance and retard as well as straight up), providing full control of camshaft set up. Both the cam and crank sprockets are machined from high grade steel - stronger than cast iron sprockets which are then matched in pairs . These sets utilize a true roller type chain made of the highest quality materials. Available in oversized sets to compensate when the block has been align bored and/or honed.