Manley Pro Series connecting rods are forged from aircraft quality 4340 vacuum degassed material. Each rod is fully machined in the Manley Lakewood, NJ factory to the highest standards. Our signature "Pro Series Lightweight" design combines the appropriate weight and rugged strength for ultimate horsepower applications. Each rod is shot peened after machining and magnafluxed. Bores are held to exacting tolerances. Bend and twist is tightly controlled. Cap fasteners are 7/16" ARP 2000 or optional 7/16" ARP Custom Age 625 cap screws.