Pros:Tremendous frequency response, ncredibly comfortable, excellent noise-cancelling properties.
Cons:Weak wire connection to the body. Easily solved with a little epoxy.
As a professional recording engineer, portable music is a big part of my life. Koss was the first (that I was aware of) company to "get it." Every predecessor to the Plug was a pathetic design (not too dissimilar from the style that comes with the iPod) where the ear bud sits outside the canal and relies on luck to keep them in position. Even with all the so-called "solutions' (foam, rubber, etc.) the damn things never stayed in place. Five years I used these ridiculous ear buds. Enter the Plug and suddenly, miracle of miracles, the ear buds stay in place with no effort - and they're incredibly comfortable. I'm not sure why all the complaints that they're uncomfortable. A soft, spongy latex pad compresses down so you can insert the Plug into your ear. The pad expands and voila!, a perfect fit and perfect sound. I've tried the ER-6 from Etymotic and Shure EC-5. Amazingly, these are better.