ARP Header Bolt Kits (400-1104)Header Bolt & Stud Kits by ARP ARP stainless steel header bolts are 15 percent stronger than Grade 8 steel. These bolts have a compact head that will allow a socket to fit into those tight, tricky spaces next to the headers. These bolts are both highly corrosion resistant and heat resistant. They have a polished finish and come in 12 point and hex style heads. Features Fastener Style: Bolt Thread Size: 3 8 in. 16 Head Style: Hex Underhead Length