These work pretty well in some equipment to keep out AC line noise, and to keep electrically noisy equipment (like a refrigerator) from polluting the AC line. E.g, I use one of these on my refrigerator. Seems to make the refrigerator run a little smoother, too! I also have one on our treadmill, which is otherwise an electrical noise-making beast.
I have a boat load of 6A Corcom filters ($12 ea), one 30A Corcom filter ($22), and four 20A Delta filters ($22 ea). Plus shipping.
