Harmonic Balancer Bolt, Hex Head Black Oxide AR134-2503Harmonic Balancer Bolt, Hex Head Black Oxidefits SB Chev 7 16 20 Thread x 2. 470" UHL With 1 2" Square Drive AR134 2503 134 2503 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 Tool * Made From Heat treated 8740