ARP Main Stud Kit for 2008 to 2019 Yamaha watercrafts. Made by ARP, the studs are 8740 chrome moly steel, heat-treated to 200,000 PSI tensile strength, and precision J-from thread-rolled after heat-treat resulting in a fastener that has threads 2000% stronger than others. This Main Stud Kit includes 10 studs, 10 parallel ground washers, 10 twelve-point nuts, moly torque lube, and an instruction sheet. ARP recommends studs are over bolts because of the abilty to obtain a more accurate torque reading studs provide over bolts. Studs don’t twist as they are fastened down. Additionally, because of this there is less force exerted on the thread of the block, which results in increased block life, especially on aluminum blocks. Finally, studs allow faster assembly and proper alignment of the caps every time. Product made in the USA.