There is a 1.5 shoe size range for each letter. They fit true to size, so if you're a women's 5.5 you would get the B. The reason this is done, is that one of the goal's of a footbed is arch support. A one size fits all footbed really doesn't allow for optimal arch support, because someone with a size 11 foot and someone with a size 5 foot when wearing a footbed, their arches would line up in different spots. So this is why there is such a narrow size range. This is a great thing though, because it allows for a very tailored fit to each person's foot, and really does what it is designed to do. Support your foot.

They are not at all one-size-fits-all. The size ranges are there (maybe they weren't before?) for men and women.

Isn't it one size fits all - cut down to size if needed?You do have to dial-in the specific letter. There are three sizes within each letter. Once you have done this, you can trim to fit.