Everything needed to strengthen the top end of your M-Eight engine. Rocker arm shafts are more durable than the stock arms. Roller rocker arms relieve additional stress caused by high-lift camshafts running and high rpm. Rocker arm stud kit extends the life of your cylinder heads by preventing damage to the rocker arm towers. Head bolt kit is made of 8640 heat-treated steel with 200,000 psi tensile strength. Sold as a kit; includes S&S rocker arm stud kit, S&S rocker arm shafts (set of 4), S&S forged steel rocker arms (set of 4) and S&S head bolt kit. Made in the U.S.A.