In terms of length, I usually wear a 6. An added bonus is that the inside part is the same color as my headphones, so it looks like they go together. I waited a while before I wrote this review because I wanted to see how this product would perform. It hasnt been that cold here in Michigan yet for the true test inside on hard wood floors. Wear lighter shoes or something. I tested the speaker?s max volume and it gets fairly loud without any distortion in the audio. Not worth $106. I did not even wear them for a run or a walk. When size 4 arrived, I couldn?t wait to try them on, which fit perfectly. I hate the earphones that completely isolate myself from the outside world, and I feel safer if I can hear the traffic when I?m walking.