All Parker Bayside Gearhead inputs are coupled to the motor shaft via the patented clamp-on split pinion design. The split-collar clamps offer holding torques 5 to 25 times greater than the peak torque of most servo motors. Due to the nature of the clamping design, maximum holding torque is achieved using a smooth motor shaft with no features such as keyways or flats. If your motor shaft has a key installed in the keyway of the shaft, it must be removed before installation of the Parker Gearhead. We DO NOT recommend mounting a Parker gearhead to a motor shaft which has a double flat. Furthermore, motor shafts which are tapered will NOT work with the clamp on pinon design of Parker Bayside Gearheads. Below is a pictorial representation of most common types of shaft features and their applicable use with Parker Gearheads.