Tone bar clips are small metal clamps that are placed on the upper treble tone bars to increase sustain. They do this by making the mass of the tone bar slightly heavier which increases the resonance of the tone bar assembly. It does this by having more mass to vibrate. It is able to achieve this without changing the tuning due to the coil on the tine below being the source of the pitch change.
If a Rhodes has notes in top treble section that have poor sustain, then adding these tone bars is an effective solution. They can often increase the decay of a note by several seconds. To install, clip the clip on to the tone band and adjust it on the tone bar to find the place that will generate the longest sustain.
Usually adding two or more tone bar clips is unlikely to make a difference to sustain. If sustain problems persist, look into replacing grommet screws, removing tone bar springs, and replacing tines.