I always wear a size UK7/EU40 and have ordered the sandals with my usual size and they fit perfectly, not sure why others have problems with sizing. My running pace is around 8 minute mile and I sweat A TON, its actually disgusting how much I sweat, now, I only mention that so you know the user type. Over-all I am pleased with my purchase. There were points putting it together I thought next time I?m just buying wood and building my own! But its nice to know its there in case I need itIts does connect to other Bluetooth speakers for more sound, I have the M71 of this brand also. Soft, comfortable and nice sole. I didnt give them a rating on battery life but after using them for a week ill come back to revisit my review and rate it. I love using these for my video shoots. No bass though but what do you expect for $10 earpod clones? Only time will tell. I usually wear between an 8 and 8-1/2 so I took a gamble on the 8 and they fit perfect.