Pros - Once set you never have to worry about it.
Can be used AC or DC current as well.
Very Sensitive temp variations.
Cons - Manual and has an external setting screw that can get in the way.
As stated in another review "The wafer has been around for a long time and works very well". Probably better than any other mechanical system I have seen or DIY McGyver(ism) Manual/Mechanical control unit you can dream up!
The fact of this design is that it is not a brand specific item. You can usually find it in other brands. Of course no matter which name brand you buy the unit only "automatically" controls the flow of electricity (On/Off) so you will need a good calibrated thermometer to set the temps to the correct settings.
What many people overlook about this mechanical wafer system is the fact that its micro switch is universal and will work with AC and DC currents. The mechanics of the wafer (round disc) is what controls and will trigger the micro switch which only makes an ON/OFF type action by way of contact to complete a circuit. Thus the switch does not care which type current (AC or DC) you decide to use. It Dose have a voltage rating so I would not hook up 220ACV to the small unit; So stick to a maximum of 110 volts AC (or) 12 or 24 volts DC. The best practice is to hook up the Neutral wire to the unit, or if using DC the Negative.
As another review stated "even some digitals incubators have this type unit as a backup", I guess the wafer back up is (as I mentioned) for DC use in case the power goes out. When a power outage 5 or more hours, you will need a DC heating system,12 volt car battery, and a good calibrated thermometer to go by. The only other alternative is to buy a gas powered AC electrical generator. Your choice but either way, this units is very versatile, dependable and highly accurate once set.