ARP 250-4301 head stud upgrade, replacing the factory head bolts. Fits the 2011-2019 Ford F-250/F-350/F-450 pickup and F-350/F-450/F-550 cab and chassis 6.7L Power Stroke. Add-on for our remanufactured 6.7L Power Stroke long block; installed on the engine before shipping only (not sold loose, since fitting studs means pulling the heads).