Great concept, but faulty beyond belief. The first day I tried them they were quite good. It took a little adjustment to get use to having this plugs in my ear (but more comfortable than the Koss "Plug" I used previously). Sound quality was quite good and a good amount of external sound (loud train noises, rude people talking at the top of their lungs on trains, idiots screaming into cell phones, etc) was blocked. But, by day two, I had to start turning the volume on my portable all the way up to get any appreciable sound (same problem occured on on PC).Also, the earbuds fall off much too easily (this should not happen in three days of use). I'm going back to KOSS.