These 4140 steel connecting rods are an exact replacement for stock M57 connecting rods with factory pistons. Made 100% in house on our cnc's with Ampco-45 small end bushings supplied by PPP Center. They are designed to hold well over 1000hp and include 3/8" ARP bolts. Weigh matched to +/- 1 gram per set. FEA analysis image is for a 35K lb load applied to the connecting rod which corresponds to 4075psi cylinder pressure.