If youre not sure, or in between sizes, get the smaller one- it stretches. Let me start off with saying those concerned aboutthe Alexa integration because of Amazon, it doesnt even come preinstalled. Rather like wearing a flip flop and a little wide, but cute enough to ignore the downsides and keep, especially at this price. Slipped the straps over my phone (easy enough), clamped it down on my handle bars (easy enough) then slid the round circle into the slot. I would not get these for any strenuous activities. the pattern is adorbs and i lovee them. A downside is that since I can?t use the lower belt yet, the upper belts push down on my lower and make them bulge. He compared them to his custom in-ears priced at $600 and thought these ones held up really well in comparison to his in-ears. I talk on it all the time and every can hear me great. We super glued it.