The Ultra Pro Magnum Roller Rocker Arms for Chevy V8 348-409 applications not only live up to the lofty standards of the original Pro Magnums, but they also take stud mount rocker performance, stability and value to a whole new level. These rocker arms feature a 3/8" stud diameter and 1.7 ratio. The 8650 chromemoly material and arched, web-like design deliver increased strength and rigidity while still reducing the moment of inertia and optimizing the dynamic balance. A unique black oxide exterior finish helps prevent corrosion and increases durability. Featuring oversized trunions, precision-sorted needle bearings and hardened roller tips for the ultimate in performance and dependability. Optimized retainer and valve spring clearances allow for use of most diameter springs, retainers and +.050" locks without clearance or fitment issues.