Mr. Gasket Headlock Locking Header bolts eliminates the need for lock washers. The serrated teeth grip header flange surface providing a locking action to maintain consistent header bolt clamp-load. Made from high-grade stainless steel Grade 8 bolts with 150,000 PSI tensile strength they are both strong and will resist rust and corrosion. The thread-lock patch prevents header bolt torque loss, provides positive thread seal and locking action in severe duty engine vibration and heat cycle conditions. The combination hex/socket head design makes installation easy and a hex tool is included.