Flywheel bolts play an important role in the performance and safety of race cars and street machines alike. Thats why the fastener experts at ARP developed special bolts that are far superior to OEM hardware. Originally developed for NASCAR Winston Cup competition, this Pro Series Flywheel bolt kit is forged from aerospace alloy, rated at 200,000 psi, and heat-treated prior to thread rolling and machining. It features an exclusive, flat, 12-point head design and larger than stock shank diameter for increased strength and improved flywheel register. Designed for select Chevrolet applications (V8 w/Tilton flywheel, uses 1/2" socket), the under head length is .875 and the thread size is 7/16-20.