I researched out this purchase pretty hardcore before I bit, and it paid off. These are almost the only headphones on the market today that are truely designed with runners in mind. They're sweatproof, they fit sturdy on the head, and they don't bounce around and aren't cumbersome. The only downside is you MUST wear your phone or bt pairing device on some sort of armband to get these to work at 100%, otherwise, if you put it in your back pocket or likewise the signal cuts out often, which can be very, very frustrating to someone who can't figure out what the problem is (hint: it's printed in big bold letters in the equipment manual) Don't expect to get stellar call quality out of the built-in mic either, especialy on a windy day, but it does its job and itsn't the worst built-in mic I've ever used (read: passable) The sound is clear from my mp3 phone and I would very much reccomend this to the workout enthusiast looking for a sturdy wireless headphone solution.