They seem to fit tight, but not over tight for the various shoes. I ended up returning these and spending the $90 on some almost identical shoes by INC at Macy’s with great padding that did not rub my Achilles. The instructions did not specify the size of the nuts, but they are larger than 1 inch so unless you have large sockets, you will need an adjustable wrench. I will update my review in a few weeks. Unfortunately my love for the shoe is overshadowed with the glaring reality that they werent built nearly as well as Clarks that I have owned in the past. This is the shoe. Battery should be full. (Same with my 3 sons teva flip-flops). 🛑🚫 STOP 🛑 🚫 SPOILERS 🚫🛑🙌👏 OMG 😲 WOW 😮 ! Within 30 minutes of hanging a towel up, the hook and the towel were on the ground.