These knobs replace the standard light switch knobs, reverser handle, and bell button on the ProtoThrottle with more accurate representations of controls from EMD control stands. 

The handles are printed in a tough grey engineering plastic, and are sold unpainted.  They can be painted by the user to match a particular prototype.  Typically the light handles were black with an inlaid white arrow and a silver or rusty center screw, the bell button was brass, and the reverser would vary based on brass or plastic and era/railroad.