DESC: Koss's innovative stereophones are designed to reduce outside noise so that you can enjoy full sounding music at a lower volume. These earphones make use of an ear-cusioning material that slowly expands in your ear canal to provide a custom fit and isolate your music from outside sound. Low impedance operation makes "the Plug" easy to drive from portable playeres, and they boast an impressive frequency responce at a rock bottom price. These are quite simply the best deal available in noise reducing, low cost earphones!