ARP's premium grade header bolt kit is an excellent choice to facilitate the installation of your vehicle's exhaust headers. To maintain a reputation for "zero defects", ensure optimum quality control, and produce fasteners of exceptionally high quality, ARP controls all aspects of the manufacturing process, performing all operations in-house where they can be closely monitored. ARP takes extraordinary steps to produce the very finest products of their kind on the market today. Manufactured from heat treated 8740 chrome moly steel with a black oxide finish, these bolts are rated at 170,000 psi tensile strength, which is substantially stronger than Grade 8 hardware. The 3/8" diameter bolts are traditional hex style, have a 1.000 under head length, and the 16 piece set includes premium-quality washers.