Competition Cams 1413-12 Magnum Roller Rocker Arm For V6 Chevy applications, 10mm stud, 1.52 ratio 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 Made from 8620 chromemoly steel that will not flex