This 24T spline servo shaft is an integral part of a ServoBlock™. It possesses a ½” OD which allows it to fit inside of a ½” bore bearing. While the 525122 Servo Hub Shaft version provides threaded holes to fasten to, this model may be the more versatile option as it allows a ½” clamping hub to slide on and tighten down. Using a clamping hub not only allows for axial adjustment, but it also allows you to clock the part that’s fastened to the top without removing the servo horn.