A two-gear set is required for gear-driven cams that do not come with secondary cam gears; be sure to select the appropriate outer cam drive gear, pinion drive gear, and mounting hardware. Due to the inherent characteristics of gear drives, you may experience more valve train noise with gear driven cams; oversized and undersized pinion gears are available to help achieve correct gear lash (sold separately). Drive gear and pinion gears must be purchased separately. Made in the U.S.A.. It is the installer's responsibility to check all clearances and follow all procedures in the S&S instructions and Harley-Davidson manual..