It is for good reason that virtually every top professional engine builder relies on ARP Pro Series head for their all-out competition powerplants. Simply stated, there's not a better stud setup on the market today. For openers, 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 190,000 psi. this procedure ensures complete heat penetration and the results are far superior to those lesser quality studs from other manufacturers who just dump pieces in a basket and hope for the best. You will also note that ARP offers specially undercut studs for several engines. This procedure (done only to the shorter studs) more equalizes the "stretch" of both studs, which makes for a more consistent clamping force-and one that compensates for engine sealing! ARP head stud kits are available with your choice of conventional hex nuts or compact 12-point nuts. Premium quality parallel ground washers are also included with each kit. Clearly, they are the best on the market today, and the favorite of leading professional engine builders in all forms of racing.