Your foot slips right off the side of the one that is extra wide. These are nice but run small. I looked at the shoes (had order 2 pairs - the other one was 8. I just received the shelf. Hope there are some left for me. The unit does come with replaceable and removable buds (and sizes) so you can experiment to see what is comfortable. This resulted in several losses of smaller units over the years before I bought this one. Love these shoes. The battery:Well so far Ive clocked in the battery running about 10% per day. I usually have it off of my ear and then its perched on my head really weird.