ARP Cylinder Head Bolts, Professional Series, Hex Head, Chevy, LS1/LS6/LS2, 5.7L Kit 2004 & Up. These Pro series cylinder head bolts from ARP are cold-forged to ensure molecular integrity. They are heat-treated prior to thread rolling and machining, and are rated at a whopping 190,000 psi. The Pro series are also available with hex and 12-point heads. All kits come complete with hardened parallel washers for even load distribution and accurate torque readings. Shipping is not included. Picture is for reference only.