This is based upon my own listening of the M6 wired version. In my experience they sound uniquely different from a lot of earphones. The treble was spiked and unnatural (fatiguing and often painful for me over time) and the bass was elevated (which isn't necessarily bad for physical activity, and really isn't their biggest problem). Adding bluetooth to iems like these at a $40 markup sounds like a really bad idea. The compression of the wireless codec will only degrade the sound. I can't call out alternatives I recommend as I've never seeked out wireless earphones, but I wanted to warn of what I find to be an unacceptable sound for $70.