Complete head gasket kit minus the head bolts please specify 3.9, 4.0, 4.2, 4.6 when ordering. Upgrade to ARP head stud kit with your next head gasket job. ARP uses a premium grade 8740 alloy that is rated far superior to "aircraft" quality. Then each stud is placed vertically in special racks and precisely heat treated to 200,000 psi. This procedure ensures complete heat penetration and the results are far superior to those lesser quality studs from other manufacturers. Also Remember, studs provide more accurate and consistent torque loading.