These small resistors convert 3-pin fans from 12 volts to approximately 5 volts. This basically means it reduces the speed of your 3-pin fan, which in turn reduces the noise the fan makes. We tested a 92mm fan and without the resistor installed, the fan ran at 2700 RPM. The RC100 would reduce the speed of the fan to around 1100 RPM, making the reduction in fan noise significant.
Fitting the resistor is very straightforward. Just plug the 3-pin fan into one end of the resistor and then the other end connects directly to your motherboard.
NOTE: The resistor reduces the RPM of the fan, in turn this reduces the air flow that the fan produces. Please bear that in mind when purchasing one of these resistors.