Competition Cams 17021-16 High Energy Die Cast Aluminum Roller 1.7 Ratio, 7/16" Stud Diameter Rocker Arm for Big Block Chevrolet Cost effective aluminum construction provides superior strength to weight ratio Needle bearing fulcrum and roller tip reduce friction and lower oil temperatures for improved response and horsepower Durable design increases valve lift while withstanding the rigors of moderate race use Die-formed aluminum body is larger than stock, and may require modifications to stock valve covers for clearance.