This pair of serrated discs work together to create a positive locking joint, as seen in the Black Magic frames and Stallion swinging arms. Very useful to the machine builder who can weld. Each half of the set is a steel disc machined with radial v-grooves every 6 degrees, providing 60 locking positions in a full rotation. Designed for a 3/8-16 threaded bolt, one side features a through hole and the other a threaded hole. Application requires reasonably precise welding to a steel base component.