If it's a voltage stabilizer it's different to the Zone VI Stabilizer, which is primarily used to stabilize the light output which varies quite a lot with temperature. You are probably aware that the temperature of a standard cold light head rises rapidly when it's switched on. The light output also rises quite markedly. The Zone Vi Stabilizer unit would also be of some use in controlling light variation due to mains voltage variation too, of course.

Interestingly (for me at least) the tubes in my recent Aristo VCL4500 cold light head (two tube VC unit) give some light increase with a rise in temperature but not a lot, but further rises in temperature cause a decrease in light, so to some degree they are self correcting. I have read that the recent Aristo tubes for single tube heads that are spectrally suitable for VC filters are also less sensitive to temperature.