The PC design consists of a magnet and armature assembly and requires a brush-holder (available from Warner Electric) to carry current from the power source to the rotating magnet.
The SF design consists of a bearing mounted magnet assembly, or field, a rotor assembly, and an armature assembly. The bearing mounted field does not rotate which eliminates the need for a brush-holder.
Armature assemblies are available in clockwise or counterclockwise rotation,and with either a hub or flat leaf springs for mounting the output device. Hardware to mount the clutch to the shaft, including bearings, may be customer supplied, or Warner Electric will be pleased to work with your engineers to supply a complete, ready-to-mount packaged solution.