Chance Standard Kelly Bar Adapters have 6 holes for 1/2'' bolts on a 5-1/4'' bolt circle and come with (6) 1/2'' grade 5 bolts, nuts, lock washers and bent arm pin with coil lock. Tough One® Kelly Bar Adpaters have 12 holes for 5/8'' bolts on a 7-5/8'' bolt circle. Comes with (12) 5/8'' grade 2 bolts, nuts, lock washers and bent arm pin with coil lock.