Competition Cams 1411-16 Magnum Roller 1.72 ratio, 7/16" Stud Diameter Rocker Arm for Big Block Chevy, Boss 302, 351 Cleveland and 429, 460 Ford Ultimate street rocker designed for serious performance enthusiasts Constructed from 8620 chromemoly steel, a superior material that will not flex and assures maximum lift Roller tip reduces friction while stiff design and superior ratio accuracy yields more effective valve lift 15 to 30 horsepower increase over stock rocker arms Use in any applications with less than 350 lbs. open spring pressure