Used for a CD player. I had them in stock, intending to use them for surround speakers, amplifiers, etc. There are several sets. The effect is tremendous. Three-dimensional, realistic sound, improved resolution, enhanced sound focus, and expanded S/N ratio. I think this is an amazing product that is in a class of its own compared to other companies' insulators. 4 sets This is a bargain, with a list price of 198,000 yen (excluding tax).