ARP's Harmonic Damper Bolts safety keep the damper locked into place as the crankshaft flexes and twists and the harmonic damper absorbs incredible amounts of kinetic energy. These damper bolts are ultra strong, 190,000 psi tensile strength that exerts maximum clamping force and are made from heat-treated 8740 chrome moly steel with heavy-duty black oxide finish. Available with a 12-point or square drive head.