This Magnum Roller Rocker Arm for Chevy V8 265-400 and V6 200-262 Applications is the ultimate street Rocker. With a 3/8" Stud diameter and 1.6 ratio, it is designed for Serious performance enthusiasts. All Magnum Roller Rocker Arms are constructed from 8620 chromemoly Steel, which is a superior material that will not flex and assures maximum lift. Their Roller tip reduces friction, while stiff design and superior ratio accuracy yield more effective valve lift. With a 15 to 30 horsepower increase over other Rocker arms, Magnum Roller Rockers are perfect for performance Applications with less than 350 lbs. open spring pressure. Don't accept inferior products or cheap knock-offs, look for the COMP Cams logo stamped into the underside of every Magnum Rocker.