ARP Header Bolt Kits | Multiple Chevrolet Fitments (434-1201)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: M8 x 1. 25 Head Style: 12 point Underhead Length