This is a "ARP 12 Point Balancer Bolt" for a 1986 or 1987 Buick Grand National, T Type, Turbo T, or GNX.
Harmonic Balancer Bolt, Chromoly, Black Oxide. As the crankshaft flexes, the balancer absorbs incredible amounts of energy. ARP balancer bolt kits will ensure that your balancer is locked into position. They feature a 12-point head that accepts a deep socket to eliminate the fear of stripping the head.
