I have a Sumiko FluxBuster. I think it's primarily for MC cartridges as it is supposed to demagnetize the coils that move through the magnetic field to produce sound. Those coils can get magnetized (moreso in some cartridges I think?), leading to sound that is less lively and somewhat dull. I have a 30+ year old Monster Alpha-2 is well known to benefit from demagnetizing. I picked up the fluxbuster because the Alpha-2 was sounding a bit lifeless. After flux busting the high end was clear and more present, bass was tighter and dynamics were improved. I know that a lot of people seem to think that this process is hooey, but I sure was impressed with what it did for my cartridge.