Material: -1Finish: BlackSmall Block Ford 239, 256, 272, 292 Y Block (Rod marked ECZ) , Small Block Ford 312, ARP 154-6004 Connecting Rod Bolts, High Performance Series, 8740 Chromemoly Steel. ARP Hi-Performance Connecting Rod Bolts are 190,000 PSI, A premium grade 8740 alloy chrome moly steel is used to manufacture ARP High Performance connecting rod bolts.This material is heat-treated to provide a tensile strength in the 200,000 psi range, which is substantially stronger than the OEM bolts. Cycle testing shows ARP High Performance rod bolts to be nearlyFive times more reliable than stock bolts.