Harmonic Balancer Bolt, Hex Head Black Oxide AR154-2502Harmonic Balancer Bolt, Hex Head Black Oxidefits Ford 351 Cleveland & Holden 253 304 308 5 8 18 Thread x 1. 800" UHL With 1 2" Square Drive AR154 2502 154 2502 Arp Offers A Special Version O f Its Rugged Balancer 200,000 Psi Rated Balancer Bolt That C an Accept Standard 1 2 Drive R atchet Or Breaker Bar To Facil itate Rotation Of The Crank As sembly. * 1 2 Square D rive Forged Into Bolt Head, En abling The Rotation Of An Engi ne With Any 1 2 Drive