For 99-17 Twin Cam. HP+® AND RACE SERIES® ADJUSTABLE PUSHRODS. .95" Wall Thickness. Maintains maximum valve lift; increases stiffness and column rigidity. Maximizes valve-train stability to increase engine rpm, horsepower and torque output. Minimal adjustment parameter eliminates flex and loss of valve-train stability problems. Individual length intake and exhaust pushrods keep the adjustment extension to a minimum. Designed to exceed performance engine needs using larger lift cams and high spring pressures while maintaining proper and critical oil flow to top-end valve train. Made from CNC-machined 7/16" tapered 4130 chromoly steel tube; 32 thread per-inch adjustment. Double jam nut lock system. HP+ pushrod wall thickness of 0.095"; Race Series wall thickness of .120". Can be used with hydraulic or solid lifters and street or race engines; "Race" Series recommended when extreme spring pressures are used. Feuling pushrods can be used with factory pushrod tubes. Made in the U.S.A.. NOTE: To ease installation on Twin Cam applications use Pushrod Tube Kit PART #s 0928-0016 or DS-193758; not required. NOTE: Requires removal of rocker covers and rocker arm supports for installation. - Part Number - 0928-0009