(RB20/25 DET head stud kit) Built for the (89-98) Nissan Skyline.Obtaining the optimum cylinder head-to-block sealing is especially critical in small displacement engines employing high compression pistons or power adders like turbochargers, nitrous oxide and superchargers. Thats why ARP head studs are popular among leading Sport Compact/Import racers.You should know that ARP uses a premium grade 8740 alloy that is rated far superior to 'aircraft' quality. Then, each stud is precisely heat-treated to 200,000 psi. Following heattreat, each stud is centerless ground to make it as close to perfectly concentric as possible. This procedure involves about ten very slight cuts and results in an exceptionally straight part. Its important to note that lesser quality studs are not even centerless ground the material is thread rolled in bar stock form (mostly before heat-treat, when the material is easier to machine). Because ARP studs are manufactured to such exacting tolerances, you will not