Direct replacement for the stock head bolts and cylinder studs. Quality is much higher and recommended for performance builds. Complete kit. Head bolts: - Black oxide coated - Heat treated 8640 steel - 200.000 psi ultimate tensile strength - 9/16" 12 point head with integral washer - Formed threads - Cold formed head - Re-usable cylinder studs - 4140 Chrome Moly - Oil quenched and tempered to 39-44 HRC - 180,000psi Tensile Strength - Rounded thread roots, rather than flat, improving fatigue strength - Positive stop shoulder allows for consistent installed height