COMP Cams 4542-16 Magnum 3/8" Stud Diameter Rocker Arm for Oldsmobile Applications For Oldsmobile V8 applications Designed for ultimate strength and locking force Magnum studs are best for street performance applications 3/8 inches stud diameter and 1.520 inches effective length 5/16 inches base thread diameter and .580 inches base thread length