I chose my usual size, but Amazon told me "nope we think you want one size smaller, based on your history and our data for this product".
They usually have something like "If you are a 10.5 for Adiddas, then you are a 10 for us" kind of thing.
Those have worked for me.
I chose my usual size, but Amazon told me "nope we think you want one size smaller, based on your history and our data for this product".