5 and it fits perfect with no socks. Even with the issue with the straps, I cant deny that this bag survived the entire road trip unscathed. There is no padding for your Achilles, I was in pain for a week after wearing them one time. While I?ve questioned the design of some previous KZ models with ZS10 pro they went for their own original look and they did a fantastic job! It works for what purpose Im looking for. Looking for alternatives to surgery I came across this product. I didn?t realize they would have such an awesome case! So If I find something else , this one will go back to amazon. The width is a bit on the narrow side, but the upper is just mesh so it fits ok. The front strap isnt as tight as I need it to be so my feet also slid forward overhanging the sole.