The reviews on these headphones is all over. I think there might be a good number of imperfect sets on the shelves. That's no bueno. I bought these headphones recently. It took a bit to figure out the right size ear thingy so that it stays in my ear. Got it. I still didn't think they sounded as good as they should from both sides. It sounded like an echo from background noise in one side. I'm a sweaty girl at the gym, and this type inside-the-ear buds have never worked, because they slip out a lot. This pair with the hook takes care of that. On the seventh day in a row of use, I kept readjusting, thinking they were slipping out, because I couldn't hear as well. That wasn't it. The left one quit working. They're sweatproof, right, so it shouldn't be a short because of that. I do like the design, so I decided to exchange them for the same product. This set is way better. They sound great. They fit great. No sweaty slipping, and the sound is great, clear and balanced, even into the second hour of cardio workout. Seems that there may be a quality control issue, considering the performance reviews are inconsistent.