The XTRM’s seem to fit pretty true to sizing for most people. They are not super wide in the toe box, but they are not narrow either. Most people are OK with going with their standard size shoe, or the the size that most shoes fit comfortably.
If you are normally between 1/2 sizes, we recommend you go up one 1/2 size.
The XTRM’s will feel a little stiff and/or tight at first. Keep that in mind as you are trying them on inside at home.