The ARP Custom Age 625 series head studs are the ultimate head stud for high horsepower and competition engines. Rolled threads after hardening, centerless ground, and clamping force rated at 260,000 PSI, the Custom Age 625 head studs are engineered to be the best option on the market to keep cylinder heads from lifting under the most demanding cylinder pressure. Inner head bolts included. Proudly made in the USA at ARP's facility in Santa Paula, California.