Product review (5 stars): Delighted with this purchase which saved my refrigerator.
This device saved my refrigerator, a 2000 unit. After a while, when the compressors get older, they don't want to start. You can hear the compressor start relay clicking, and the compressor gets warm, but you can't feel its vibration when you place a hand on it. Some of these units (like mine) come from the factory with neither a start capacitor or a run capacitor. The Supco units include one or both (I've never taken one apart.

In particular, the RCO series (RCO41 for full-size refrigerators, RCO81 for "dorm" refrigerators) are called Hard-Start Kits. They apparently have capacitors with greater capacitance, to give the compressor an extra kick at startup and will get that hard-starting refrigerator cooling again.

This unit includes the start relay, the overload protector (PTC), and capacitor(s) and costs LESS than a replacement relay and overload.

I recommend this device which worked when a new relay and overload did not.