For use with low output humbucker when coil splitting. Humbuckers with lower than 10k output when split will produce an output that is much lower then a traditional single coil pickup. That along with the dimensional differences of the bobbins the result is often times a drop in volume and a thinner sound overall. By adding an inline resistor to the circuit it allows for some of the signal to remain resulting in a partial split. You will still get a single coil tone with some 60 cycle hum and all the good stuff that comes with single coil pickups without loosing the volume. A fantastic and often times highly recommended mod.