Pro Series Bolts Are Cold Forged To Ensure Molecular Integrity, Heat Treated Prior To Thread Rolling And Machining Nominally Rated At 200,000 PSI Tensile Strength These Fasteners Deliver Superior Strength And Meet The ARP 'Zero Defect Zero Failure' Quality Standard Bolts Have A Reduced Wrenching Hex Or 12 Point Head And Wide Area Flange To Eliminate The Need For Valve Train Removal For Cylinder Head Retorquing And Permits The Use Of Larger Diameter Valve Springs