The fins are a heatsink for the transistor inside the fsr. Why they call it a Final Stage Resistor is beyond me. The small wire that you see in the harness is the control voltage wire that controls the internal transistor. The internal transistor is attached to the housing to dissipate heat. The heater fan blows air across this heatsink to further cool it. If my unit fails again, I will hollow out the case and design a pwm fet controller that will handle higher current. When and if this happens, I will post pics and a possible schematic.