After reading another reader's review, I got a size L (32"-35") to wear around my hip (37") for running. This belt did exactly what it said it wouldn't - it bounced and it rode up. I took my phone out to see if it would help with the bouncing and riding up, but even with just my key (so, basically nothing in the belt), it still rode up. 2 miles into my run, after constantly having to adjust this belt, I just took it off and hheld it for the rest of my run. Now I can't tell if this is just a terrible product or if they're just terrible with sizing. I will order the medium and see how it goes.